JP2010070430A - Conductive nitride semiconductor substrate and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive nitride semiconductor crystal substrate which is almost free from warp and hardly generates cracks, and to provide a method for manufacturing the same. <P>SOLUTION: This self-standing conductive nitride semiconductor substrate having a specific resistance r: 0.0015 Ωcm≤r≤0.01 Ωcm, a thickness of ≥100 μm, and a warp with a curvature radius U: 3.5 m≤U≤8 m is obtained by forming a mask, in which dot coating parts or stripe coating parts having a width or a diameter s of 10-100 μm are arranged at an interval w of 250-10,000 μm, on a ground substrate, then growing a nitride semiconductor crystal on the ground substrate by an HVPE (Hydride Vapor Phase Epitaxy) method comprising supplying a group 3 raw material gas and a group 5 raw material gas, wherein the ratio of the group 5 raw material gas to the group 3 raw material gas is 1-10, and a silicon-containing gas at a growth temperature of 1,040-1,150°C, and removing the ground substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a conductive nitride semiconductor substrate and a method for manufacturing the same. A nitride semiconductor refers to gallium nitride (GaN), aluminum nitride (AlN), indium nitride (InN) and mixed crystals of InGaN, AlInGaN, and the like. The target is not a thin film attached on the base substrate but a self-supporting crystal substrate. Here, GaN is mainly described. Since gallium nitride (GaN) has a wide band gap, it is used as a material for blue light-emitting elements.

Conventionally, light emitting elements such as blue light emitting diodes and semiconductor lasers have been manufactured by epitaxially growing nitride semiconductor thin film crystals such as InGaN, GaN, and AlInGaN on a sapphire single crystal substrate (α-Al ₂ O ₃ ). . Sapphire is the same hexagonal system as gallium nitride. A GaN C-plane thin film is grown on the sapphire C-plane crystal.

  However, the sapphire substrate is insulative and the n-electrode cannot be taken from the bottom. Since the cleaved surface of GaN and the cleaved surface of the sapphire substrate are different, chips must be separated with a cutting machine. There is a problem that it takes time and effort and the yield of chip separation is poor.

  Also, the lattice constants of gallium nitride (GaN) and sapphire are quite different. GaN grown on a sapphire substrate has a large dislocation density. The warpage is also large. Therefore, in order to use gallium nitride itself as a substrate, an attempt was made to produce a substrate crystal with gallium nitride. Gallium nitride has been considered as a suitable material for blue light-emitting elements because of its wide band gap. In the case of a light-emitting element, it is convenient to take an n-electrode on the bottom and a p-electrode on the apex, so that a highly conductive substrate is desired.

  In the manufacture of nitride semiconductor substrates, the growth of n-type nitride semiconductor crystals having a high free electron density has been aimed at. At present, it is possible to manufacture an oxygen-doped n-type GaN free-standing substrate having a diameter of 2 inches.

When a nitride semiconductor thin film (GaN, InGaN, AlGaN thin film) is formed on a sapphire substrate in order to manufacture a light emitting element, the MOCVD method is often used. Since it is a gas phase synthesis method, the raw material is given in the form of a gas. Nitrogen is provided in the form of ammonia (NH ₃ ). The MOCVD process gives Group 3 elements in the form of organometallics. A Group 3 element organic metal such as gallium or indium (trimethylgallium, triethylindium, etc.) and NH ₃ are used as raw materials and supplied onto a heated sapphire substrate.

  The HVPE method is often used to produce a GaN-based semiconductor thin film by a vapor phase synthesis method. In this method, a Ga boat containing a Ga metal melt is provided on a susceptor, and HCl is blown to synthesize GaCl, which is used as a Ga raw material. Accordingly, the source gases are GaCl and ammonia.

  In Patent Document 1, a GaN buffer layer is formed by attaching a mask having a window diameter of 1 to 5 μm and a window pitch of 4 μm to 10 μm on a GaAs substrate, and GaN is formed thereon by MOCVD at 820 ° C. or 970 ° C. A method is described in which a thick GaN crystal is obtained by C-plane growth by HVPE at 970 ° C., 1000 ° C., 1010 ° C., 1020 ° C., and 1030 ° C.

  Patent Document 1 uses a mask having a fine window. FIG. 1 shows a plan view of an example of a mask. A mask is provided on the base substrate U. The mask is such that many small windows W are regularly arranged in a wide continuous covering portion M. The base substrate U is exposed from the window W. The area of the covering portion M is much larger than that of the exposed portion E (window W). The covering portion M is a single thin film that is continuous and has the same spread as the base substrate U. There are many exposed parts E (openings: windows W), but the total area is small.

  The principle of dislocation reduction by the mask method will be described with reference to FIG. 2 (1) to 2 (7) are cross-sectional views showing the state of crystal growth by the mask method. As shown in FIG. 2 (1), the mask M is formed by forming a mask material on the base substrate U and regularly providing small windows W (exposed portions E). When gallium nitride is vapor-phase grown, a gallium nitride crystal G is formed only in the window W (exposed portion E). In the exposed portion E, many upward dislocations T are generated at the boundary between the crystal G and the base substrate U (FIG. 2B).

  As the growth proceeds, a part of the crystal G on the exposed portion E (window W) rides on the covering portion (mask) M and extends laterally on the mask M (covering portion) (FIG. 2 (3)). )). Since it grows in the horizontal direction, the dislocation T also extends in the horizontal direction. The lateral surface is facet F with a low index. As shown in FIG. 2 (4), the crystal G extends in the upward and lateral directions and has a truncated cone shape. The upper surface of the table is a C surface (C). As shown in FIG. 2 (5), crystals extending from adjacent windows come into contact. The dislocations T extend sideways and collide with each other. As a result, some dislocations cancel each other.

  As shown in FIG. 2 (6), the groove of the facet F is filled and becomes smaller. Eventually, the concave portion formed by the facet is filled to form a flat surface C. The flat surface is a C plane. Thereafter, the growth is continued with the flat C-plane as the surface. The dislocation T is large on the window W (exposed portion E) and small on the covering portion (mask) M.

Patent Document 1 is an important conventional technique because the growth temperature, the raw material partial pressure, and the like are specifically shown. Reference 1 describes the growth temperature as follows. In the case of the HVPE method, the growth temperature is 970 ° C., 1000 ° C., 1010 ° C., 1020
And 1030 ° C. In the case of the MOCVD method, the growth temperatures are 820 ° C. and 970 ° C.

In the HVPE method, the raw materials are HCl, Ga melt, and NH ₃ . The Group 3 raw material is made GaCl by reacting Ga melt with HCl gas. The amount of the Group 3 material and the Group 5 material to be supplied is expressed by the partial pressure P _{GaCl of GaCl 3 and} the partial pressure P _{NH3 of} NH ₃ . Here, the partial pressure unit is Pa, but 1 atmosphere (1 atm) is approximated to 0.1 MPa (100,000 Pa). The unit is often kPa (1000 Pa), but it is an approximation of 100 kPa = 1 atm. The ratio b of the Group 3 and Group 5 materials can be expressed by the ratio of the NH ₃ partial pressure P _NH3 and the GaCl partial pressure P _GaCl . The group 5 and group 3 raw material ratio is referred to as group 5/3 group ratio b. It is defined as b = P _NH3 / P _GaCl .

  Patent Document 1 states that the specific resistance r of a GaN crystal made by a mask method is in the range of r = 0.005 Ωcm to 0.08 Ωcm.

  The substrate temperature during growth and the 5/3 group ratio b are important conditions that define crystal growth. FIG. 22 shows a list of the growth temperatures and the 5/3 group ratio b of all Patent Documents 1 to 11 described below. The horizontal axis represents the substrate temperature (° C.), and the vertical axis represents the 5/3 group ratio b. The coordinates of the substrate temperature of GaN and the 5/3 group ratio b shown in the patent document are circled. The black circle is based on the HVPE method, and the black dot white circle is based on the MOCVD method. The numbers attached to the black circles and black dots and white circles are the numbers of patent documents. The growth conditions by the MOCVD method described in the example of Patent Document 1 are as follows.

The growth temperature Tq, NH ₃ partial pressure P _NH3 , TMG partial pressure P _TMG , and _5/3 group ratio b are shown in this order.
970 ° C 20 kPa 0.2 kPa 100 times
970 ° C 25 kPa 0.2 kPa 100 times
820 ° C 20 kPa 0.3 kPa 67 times
970 ° C 20 kPa 0.2 kPa 100 times
1000 ° C 20 kPa 0.4 kPa 50 times
970 ° C 25 kPa 0.5 kPa 50 times

The substrate temperature by MOCVD method of patent document 1 is 820 to 1000 ° C., and the 5/3 group ratio b is 50 to 100 times. These are represented by five black dots and white circles at the height of the left half of FIG. The third portion of 820 ° C. and 67 times is omitted because the temperature is too low to enter FIG.
The growth conditions by the HVPE method described in the example of Patent Document 1 are as follows.

The growth temperature Tq, NH ₃ partial pressure P _NH3 , HCl partial pressure P _HCl , and _5/3 group ratio b are shown in this order.
970 ° C 25kPa 2kPa 12.5 times
970 ° C 25 kPa 2.5 kPa 10 times
970 ° C 25 kPa 0.5 kPa 50 times
1000 ℃ 20kPa 2kPa 10 times
950 ° C 25kPa 2kPa 12.5 times
1020 ° C 25kPa 2kPa 12.5 times
1000 ° C 25 kPa 2 kPa 12.5 times
1010 ° C 25kPa 2kPa 12.5 times
1030 ° C 25kPa 2kPa 12.5 times
In the HVPE method of Patent Document 1, the 5/3 group ratio b is 10 to 50 times at a substrate temperature of 950 to 1030 ° C.

  In Patent Document 2, a mask having fine windows in a staggered pattern is formed on a GaAs substrate, and GaN is grown thickly while maintaining the C plane by the HVPE method, and the GaAs substrate is removed to have a diameter of 20 mm or more. A self-standing GaN substrate having a thickness of 70 μm or more and a deflection (warpage) of 0.55 mm or less in terms of a 50 mm diameter wafer is provided. When the wafer has a diameter of 50 mm and the center deflection (warpage) is 0.55 mm, the radius of curvature R is about 600 mm = 0.6 m. Big curvature.

Patent Document 2 970 ° C. The growth temperature in the HVPE method, 1020 ° C., and 1030 ° C., the GaCl partial pressure _{P GaCl was} set to 1kPa or 2kPa (0.01~0.02atm), is set to 4kPa or 6kPa the NH ₃ partial pressure . It is stated that when the GaCl partial pressure is P _GaCl = 1 kPa, the surface is flat, but the warpage is large, the internal stress is huge, the crystal is easy to crack and cannot be used, and the film thickness cannot be 70 μm or more.

On the contrary, when the GaCl partial pressure is set to P _GaCl = 2 kPa, the surface is rough, but it is described that a crystal with small warpage and small internal stress can be formed. NH ₃ partial pressures are 6 kPa, 12 kPa, and 24 kPa. The 5/3 group ratio b is b = 3, 6, 12. The curvature radius is about 1 m. The specific resistance is 0.0035 to 0.0083 Ωcm. It is an n-type crystal.

The growth conditions described in the example of Patent Document 2 are as follows.

The growth temperature Tq, NH ₃ partial pressure P _NH3 , GaCl partial pressure P _GaCl , and _5/3 group ratio b are shown in this order.
1030 ° C 4kPa 1kPa 4 times
1030 ℃ 6kPa 1kPa 6 times
970 ℃ 6kPa 2kPa 3 times
970 ° C 6kPa 1kPa 6 times
970 ° C 6kPa 1kPa 6 times
1020 ° C 6 kPa 2 kPa 3 times
1020 ° C 6 kPa 2 kPa 3 times
1030 ℃ 6kPa 1kPa 6 times
970 ℃ 6kPa 2kPa 3 times
970 ° C 12kPa 2kPa 6 times
970 ° C 24kPa 2kPa 12 times
Both are HVPE methods. The substrate temperature is 970 to 1030 ° C., and the 5/3 group ratio b is 3 to 12 times. The growth conditions (substrate temperature, b) of Patent Document 2 are indicated by eleven black circles in the lower left part of FIG.

  Patent Document 3 discloses a mask having dotted windows arranged on a GaAs substrate at regular intervals in the [11-2] direction and shifted by a half pitch in the [−110] direction, or a stripe extending in the [11-2] direction. Forming a mask having a rectangular window or a mask having a stripe-like window extending in the [−110] direction, providing a buffer layer, and epitaxially growing GaN by HVPE while holding the C plane, and removing the substrate and the mask. A method of manufacturing a self-standing single crystal substrate of GaN is proposed.

Patent Document 3 is also a method of reducing dislocations by forming a mask having a large number of small windows arranged vertically and horizontally on a base substrate U as shown in FIG. GaCl partial pressure _{P GaCl was} in some cases 1kPa two (0.01 atm) and 2 kPa (0.02 atm). In the case of 1 kPa, it is stated that a GaN crystal having a flat surface but large internal stress, large warpage, and easy cracking can be obtained. In the case of 2 kPa, it is stated that the surface is rough, and a GaN crystal having a small internal stress and a small warp and hardly cracked can be formed.

It is said that when the growth temperature is 1020 ° C. or 1030 ° C., the surface is flat and the internal stress is large and cracks easily.

In the case of a thick crystal with a GaCl partial pressure of 2 kPa at a growth temperature of 970 ° C., it is said that a GaN crystal having a rough surface with small internal stress and small warpage can be formed. The NH ₃ partial pressure P _NH3 is 6 kPa to 12 kPa.

In summary, in Patent Document 3, the growth temperature for manufacturing a rough GaN crystal which is warped and has low internal stress and is difficult to break is 970 ° C., GaCl partial pressure is 2 kPa, NH ₃ partial pressure is 6 to 12 kPa, 5/3 group. The ratio b is about 3-6. The specific resistance is 0.01 Ωcm to 0.017 Ωcm and is n-type.

The HVPE growth conditions described in the example of Patent Document 3 are as follows.

The growth temperature Tq, NH ₃ partial pressure P _NH3 , GaCl partial pressure P _GaCl , and _5/3 group ratio b are shown in this order.
1030 ° C 4kPa 1kPa 4 times
1030 ℃ 6kPa 1kPa 6 times
970 ℃ 6kPa 2kPa 3 times
970 ° C 6kPa 1kPa 6 times
970 ° C 6kPa 1kPa 6 times
1020 ° C 6 kPa 2 kPa 3 times
1020 ° C 6 kPa 2 kPa 3 times
1030 ℃ 6kPa 1kPa 6 times
970 ℃ 6kPa 2kPa 3 times
970 ° C 12kPa 2kPa 6 times
970 ° C 24kPa 2kPa 12 times
Both are HVPE methods. The substrate temperature is 970 to 1030 ° C., and the 5/3 group ratio b is 3 to 12 times. The growth conditions (substrate temperature, b) of Patent Document 3 are indicated by eleven black circles in the lower left part of FIG.

  In Patent Document 4, double and triple ELO masks (Epitaxial Lateral Overgrowth) are alternately provided so as to reduce dislocations, while maintaining the C-plane of Si-doped n-type GaN crystals by MOCVD and HVPE. Grow. Since the ELO mask has a large dislocation density at the window and a small dislocation density on the mask, the dislocation density can be reduced by attaching double or triple ELO masks so that the windows are different. In the case of the MOCVD method, it is stated that the 5/3 group ratio b is 30 to 2000 times as a good condition.

In the example of Patent Document 4, a source gas with a ratio of 5/3 group ratio b = 12000 times, 2222 times, 1800 times, 1500 times, 800 times, and 30 times is used by the MOCVD method. The preferred growth temperature is stated as 950 ° C. to 1050 ° C. HVPE conditions are not stated. In FIG. 22, band lines of b = 2222 times, 1800 times, 1500 times, 800 times, 30 times, and temperatures of 950 to 1050 ° C. are drawn and marked with white spots. The n-type dopant is Si. Si atoms replace Ga atoms and give out one free electron. So Si becomes an n-type dopant. Silane gas (SiH ₄ ) is used for doping. First, a trapezoidal crystal is formed on the window of the ELO mask by the MOCVD method, and then the HVPE method is switched immediately before combining on the ELO mask.

  Patent Document 5 is almost the same as Patent Document 4, and proposes a device for reducing dislocations by using a double or triple ELO mask. The substrate temperature, group 3 partial pressure, and group 5 partial pressure as growth conditions are the same as in Patent Document 4 and will not be described. Although not described in FIG. 22, it may be considered that it is the same as Patent Document 4.

Patent Document 6 proposes for the first time a method of manufacturing an n-type GaN substrate by doping GaN with oxygen (O) as an n-type dopant. If oxygen substitutes nitrogen, one free electron can be provided, so that it may become an n-type dopant. However, since it is not known in advance what level oxygen forms in GaN, it cannot be predicted whether it will be an n-type dopant without actually conducting a doping experiment.
Patent Document 6 does not specifically show the substrate temperature or the raw material partial pressure. Also not written in FIG.

In Patent Documents 4 and 5, silane gas (SiH ₄ ) is used to dope the crystal with Si as an n-type dopant. Silane gas may explode and is dangerous to use in large quantities for n-type substrate growth. Patent Document 6 has found that oxygen creates a shallow donor level in GaN. When water is added to the source gases NH ₃ , HCl, etc., and an ELO mask is provided on the GaAs substrate and a GaN crystal is grown by the HVPE method, the C plane grows. An n-type carrier is generated to make the crystal n-type. Moreover, the activation rate is 100% over a wide concentration range. For the first time it has been shown that oxygen is a convenient n-type dopant for thick crystals such as substrates. Patent Document 6 only points out that oxygen can be an n-type dopant for the first time and is unaware of doping anisotropy.

  Patent Document 7 reveals that there is significant anisotropy when doping GaN with oxygen. The selectivity is such that oxygen hardly enters through the C plane ((0001) plane) and oxygen easily enters through a plane other than the C plane. In Patent Document 7, as shown in FIG. 17, on the surface, a large amount of non-C-faceted facets F that are grown in the c-axis direction on the average are produced, and oxygen is taken into the crystal through facets F that are non-C-planes. Alternatively, as shown in FIG. 18, a method of doping oxygen from the non-C surface using a GaN base substrate having a non-C surface (hkmn) (≠ (0001) surface) has been proposed. Patent Document 7 reveals the remarkable anisotropy of oxygen doping for the first time.

The HVPE growth conditions described in the example of Patent Document 7 are as follows.

The growth temperature Tq, NH ₃ partial pressure P _NH3 , HCl partial pressure P _HCl , and _5/3 group ratio b are shown in this order.
1020 ° C 20 kPa 1 kPa 20 times
This is indicated by a black circle in FIG. 22 where “7” is added to the coordinates at 1020 ° C. and 20 times.

  Patent Document 8 proposes a new dislocation density reduction method that is completely different from the ELO method (shown in FIGS. 1 and 2; growing while maintaining a flat surface C as shown in FIG. 2 (7)). In Patent Document 8, by appropriately controlling the growth conditions, a large number of large and small pits P made of facets F and facets F are actively created as shown in FIG. 3, and facets F and pits P are not embedded and facets are formed until the end of growth. To maintain. This is called facet growth because the facet is maintained until the end without embedding pits. The pit P is a hexagonal pyramid or a 12-sided pyramid.

  As shown in the perspective view of the pit P in FIG. 4 and the plan view of the pit P in FIG. 5, when growing while maintaining the concave portion (pit P) of the facet F, a crystal is formed in the normal direction V of the facet F inside the pit P. grow up. Since the dislocation T extends along the growth direction V, the dislocation T extends in the facet normal direction. The dislocation T is drawn into the boundary line B by facet growth. A set of dislocations T is formed below the boundary line B (planar defect PD).

As facet growth progresses, dislocations gather further to the bottom of pit P. A large portion of dislocations T (linear defect set: H) is formed at the bottom of the pit P. Even if the total amount of dislocations does not change so much, dislocations gather in the planar defects PD and linear defects H, so that the dislocation density in other portions decreases. Unlike the ELO method (FIGS. 1 and 2), this has an effect of reducing dislocation from the middle to the end of growth. This is a completely new dislocation density reduction method. This method is called the facet growth method because the facet is maintained and the dislocation is reduced by the action of the facet.

  Since the method of Patent Document 8 does not know where the pits P (concave portions) can be formed, it is called a random facet and distinguished from the subsequent improved type. The resulting crystals have significant irregularities on the surface.

  The growth conditions described in the example of Patent Document 8 (Random Facet) are as follows.

The growth temperature T, NH ₃ partial pressure P _NH3 , HCl partial pressure P _HCl , and _5/3 group ratio b are shown in this order.
1050 ° C 20 kPa 0.5 kPa 40 times
1000 ° C 30 kPa 2 kPa 15 times
1050 ° C 20 kPa 0.5 kPa 40 times
1020 ° C 20 kPa 1 kPa 20 times
1000 ° C 30 kPa 2 kPa 15 times
1000 ° C 40 kPa 3 kPa 13 times
980 ° C 40 kPa 4 kPa 10 times
The growth conditions of Patent Document 8 are 980 ° C. to 1050 ° C., and b = 10 times to 40 times. The 5/3 group ratio b is large. Seven black circle points having coordinates of (substrate temperature, 5/3 group ratio b) spread in the center of the lower half of FIG.

  In Patent Document 8, since the substrate has no anisotropy and specificity, the position where the facet pit is formed is controlled by chance. This is called the random facet method. Since the pit position is determined by chance, it is difficult to manufacture a device on the pit position. Since there is no local specificity, dislocations that have once gathered may re-discrete with growth. Since it is a substrate on which a device is formed, it is more convenient if the position where the facet pit can be formed can be designated in advance. If dislocations are confined and re-discrete can be eliminated, further reduction of dislocations can be achieved.

  In Patent Document 9, as shown in FIG. 6, a mask is formed on a base substrate U so as to regularly arrange isolated dot-shaped covering portions M. Unlike the ELO of FIGS. 1 and 2, the portion where the base substrate U is exposed (exposed portion E) is much wider than the covering portion (mask portion) M. The sum of the covering portion interval w and the covering portion diameter s is the pitch p. w is much larger than s. The pitch p of the covering portion array is also much larger and wider than ELO. GaN is vapor grown on the masked underlying substrate U. Growth begins at exposed part E. A thin film is formed on the exposed portion E. Since the growth is delayed on the covering portion M, a recess (facet pit P) having the covering portion M as a bottom is formed.

  Facet growth using a dot mask will be described with reference to FIGS. As shown in FIG. 9 (1), an isolated spot-shaped covering portion M is formed on the base substrate U. When gallium nitride is vapor-phase grown, a crystal G grows only on the exposed portion E of the base substrate as shown in FIG. It does not grow on the covering portion M. As shown in FIG. 9 (3), crystals accumulate on the exposed portion E. The inclined surface is a facet F with a low index. As shown in FIG. 9 (4), a faceted pit P having a hexagonal pyramid or a 12-sided pyramid having a covering portion M as a bottom and an inclined surface as a facet F is formed. As shown in FIG. 9 (5), crystals are also placed on the covering portion M. This is a closed defect gathering region H gathered at a high density of dislocations. Under the facet is a single crystal low dislocation associated region Z. The flat surface is the C surface (C). Below the C plane is a single crystal low dislocation residual region Y.

  As shown in the perspective view of the crystal in FIG. 7 and the plan view in FIG. 8, facet pits P made of facets F such as inverted conical petals are arranged vertically and horizontally on the crystal surface. A portion corresponding to the stem is a closed defect gathering region H where dislocations are concentrated. A portion corresponding to the root is a covering portion M. The flat surface is the C surface. The portion (Y) formed below the C plane is a low dislocation portion. The bottom (Z) of facet F is also a low dislocation part. In order to distinguish this from others, it may be called a dot type. This method is temporarily called a dot facet growth method.

  As described above, the facet pit P has an action of collecting the dislocations T on the facet F at the boundary line B and further collecting them at the bottom of the pit. The pit bottom (above the covering portion M) becomes a closed defect gathering region H where dislocations are concentrated. Once disassembled, dislocations are not re-discrete. Therefore, it is called “closed”. The other portions are a single crystal low dislocation associated region Z (which can be formed under the facet) with few dislocations and a single crystal low dislocation residual region Y (which can be formed under the C plane). Z and Y are low dislocations.

  According to Patent Document 9, the concept of a closed defect gathering region H, a single crystal low dislocation associated region Z, and a single crystal low dislocation residual region Y was first generated. What is formed on the mask is a closed defect gathering region H. The single crystal low dislocation associated region Z can be brought into contact with the mask on the exposed portion without the mask. It is the single crystal low dislocation residual region Y that can be positioned away from the mask on the exposed portion. The facet is generated obliquely from the mask, covers the exposed portion, and a single crystal low dislocation associated region Z is formed under the facet, which can be in contact with the mask. Since the single crystal low dislocation residual region Y is a region surrounded by the single crystal low dislocation associated region Z, it can be positioned away from the mask. Facet growth masks do not have small windows with a fine pitch unlike ELO masks. A large-sized spot-like (circle, square, etc.) covering portion M (FIG. 6) is formed in a wide exposed portion.

  In the ELO mask (FIGS. 1 and 2), the covering portion M is wider than the exposed portion E (window W), the covering portion M is continuous in one sheet, and the many exposed portions E (window W) are small (diameter). 1 to 2 μm), the pitch is small (2 μm to 6 μm), and the total area of the exposed portion E is smaller than the covering portion area.

  On the other hand, in the mask used as the basis of the facet pit of Patent Document 9, the exposed portion E is wider than the covering portion M as shown in FIG. The exposed part E is one continuous area. Although there are many covering parts M, the total area of the covering parts is narrower than the exposed part area. As shown in FIGS. 7, 8, and 9, a facet F is formed at the exposed portion E, and a portion immediately below it becomes a single crystal low dislocation associated region Z having a low dislocation density and a high quality, so that it is essential that the exposed portion E is wide. The covering portion M diameter is considerably large (diameter 20 μm to 100 μm). The top of the covering portion M becomes the bottom of the facet pit P. The facet pit P collects and captures dislocations at the bottom and does not release the dislocations again. A feature is that a closed defect gathering region H is formed at the position of the mask M, and low dislocation portions Z and Y are formed around it (FIGS. 8 and 9). Low dislocations Z and Y are formed on the exposed portion E without a mask. Z can be directly below the facet, and Y can be directly below the C-plane growth portion. Both Z and Y are single crystals and low dislocations. An HZY concentric structure is formed around the point mask. In ELO, the mask exposure portion E (window W) has high density dislocations (H) and the coating portion has low dislocations (Z, Y). The relationship is exactly the opposite.

The growth conditions in the example of Patent Document 9 are as follows.

The growth temperature Tq, NH ₃ partial pressure P _NH3 , HCl partial pressure P _HCl , and _5/3 group ratio b are shown in this order.
1050 ° C 30 kPa 2 kPa 15 times
1030 ° C 30 kPa 2.5 kPa 12 times
1010 ° C 20 kPa 2.5 kPa 8 times
1030 ° C 25 kPa 2.5 kPa 10 times
1050 ° C 30 kPa 2.5 kPa 12 times
1030 ° C 25kPa 2kPa 12.5 times
1030 ° C 25kPa 2kPa 12.5 times
The growth temperature is 1010 ° C. to 1050 ° C., and the 5/3 group ratio b is 8 to 15 times. In FIG. 22, this is represented by seven black circles with the number “9” in the middle of the lower half.

  In Patent Document 9, since the mask is in the form of isolated points (dots) that are regularly distributed, a closed defect gathering region H is formed on the dot (mask), and a single crystal low dislocation associated region Z, a single crystal is formed in the exposed portion around the mask. A crystal low dislocation residual region Y is formed. Since devices such as semiconductor lasers and light emitting diodes are formed thereon, it may be inconvenient if the closed defect gathering regions H are dispersed.

  Therefore, in Patent Document 10, as shown in FIG. 10, a mask having a covering portion M with parallel stripes at equal intervals is formed on a base substrate U, and GaN is facet grown thereon. The sum of the width s of the mask covering portion M and the width w of the exposed portion E is the pitch p (p = s + w). The s and w of this method are larger than the pitch and interval of the ELO method. When s and w are compared, w is much larger than s. GaN is grown on the underlying substrate U by vapor phase growth.

  As shown in a plan view in FIG. 11 and a perspective view in FIG. 12, a large number of parallel peaks and valleys having a flat top surface are obtained. A parallel crystal defect gathering region H is formed on the covering portion M, and a parallel low defect single crystal region Z and a C-plane growth region Y are formed on the exposed portion. A set of dislocations formed on the parallel mask is called a crystal defect collecting region H. The continuous growth under the adjacent facet is called a low defect single crystal region Z. A C-plane growth region Y may or may not be formed between adjacent low defect single crystal regions Z.

  In Patent Document 9, a defect region H is formed on an isolated point mask, which is closed and emphasized with the word “closed”. However, in the case of a stripe mask, H is closed at the end portion. “Closed” is not appropriate because there is no such thing. Therefore, what can be formed on the mask is called a crystal defect gathering region H. Since this is the same as the closed defect gathering region H of Patent Document 8, the same symbol H is given. Since the exposed part spreads continuously and Z spreads and does not necessarily accompany H, “accompaniment” is not suitable. Therefore, Z was named the low defect single crystal region Z. Since it is the same as the single crystal low dislocation associated region Z of Patent Document 8, the same symbol Z is attached. In the case of the dot mask of Patent Document 9, an extra portion is always formed by drawing a contact circle having the same radius around the mask. Therefore, in Patent Documents 8 and 9, the single crystal low dislocation residual region Y always occurs. However, in Patent Document 10, since the mask is parallel stripes, Y may or may not be possible. If there is C side, it is Y. Since it occurs along with the C plane, it is called a C plane growth region Y in Patent Document 10. Since it is the same as the single crystal low dislocation residual region Y, the same symbol Y is given.

Depending on the growth method, the C-plane growth region Y may disappear. As shown in the plan view of FIG. 13 and the perspective view of FIG. Parallel crystal defect gathering regions H are formed on the covering portion M. This is a valley. A low-defect single crystal region Z parallel to the exposed portion adjacent thereto is formed. The Yamagata facets F and F are pointed and have no C-plane part. The C-plane growth region Y has disappeared. ... ZHZH
... the structure.

  The stripe facet growth method will be described with reference to FIG.

  As shown in FIG. 15 (1), a plurality of parallel-line stripe covering portions M are formed on the base substrate U. The pitch p (20 μm to 2000 μm) of the covering portion M is much wider than the pitch of the mask windows (about 2 μm to 6 μm) in FIGS. The exposed part E is wider than the covering part M. When vapor phase growth of gallium nitride is performed, a crystal G grows only on the exposed portion E of the base substrate as shown in FIG. It does not grow on the covering portion M. As shown in FIG. 15 (3), the crystal G is stacked on the exposed portion E. The inclined surface is a facet F with a low index. The crystals G are in the form of parallel stripes delimited by the covering portion M. As shown in FIG. 15 (4), V-grooves having parallel inclined surfaces with the covering portion M at the bottom and inclined in the opposite direction are formed in parallel. Opposing inclined surfaces are facets F and F having the same angle but opposite inclination directions. A flat surface between adjacent masks is a C surface (C).

Eventually, crystals will also be placed on the covering portion M as shown in FIG. This is a crystal defect gathering region H in which dislocations gather at a high density. Furthermore, crystal growth proceeds as shown in FIG. The crystal defect gathering region H on the mask M extends upward with the size as it is. The parallel facets F, F are wider. Immediately below the facets F, F is a low defect single crystal region Z. The boundaries between the crystal defect gathering region H and the low defect single crystal region Z are the crystal grain boundaries K and K. The crystal grain boundaries K and K confine the dislocations in the crystal defect gathering region H.

The flat surface in the middle of the mask is the C surface (C). Below the C plane is a C plane growth region Y. The C surface (C) becomes gradually narrower. The pitch of the crystals forming the stripe structure is equal to the mask pitch p. The mask pitch p is the sum of the mask width s and the exposed portion width w (p = s + w). When the crystal growth further proceeds, parallel crystals such as mountain ranges with the crystal defect gathering region H as the ridge and the C plane as the ridge as shown in FIG. The C-plane portion (C) that hits the summit becomes narrower. Immediately below the facet F is a low-defect single crystal region Z, and directly below the C plane is a C-plane growth region Y.

In some cases, the crystal grows upward while maintaining this shape. Or it may look like a parallel mountain range with even sharper peaks. FIG. 16 (2) shows such a case. In this case, the C plane is eliminated. The C-plane growth region Y is also lost.

According to Patent Document 10, a structure of ZHZYZHZYZH ... or a structure of ZHZHZH ... can be formed in parallel. Dislocations concentrate on the crystal defect gathering region H, and the low defect single crystal region Z and the C-plane growth region Y are single crystals and low dislocations.

The method of Patent Document 10 can be called a stripe-type facet growth method because a mask is formed in parallel and a crystal defect assembly region H is formed in parallel. This is because the low-defect single crystal regions Z are arranged in a straight line, so that devices such as semiconductor lasers and light-emitting diodes can be easily produced.

  The facet growth method and the ELO method are completely different methods. The shape, dimensions, and action of the mask are also different. The ELO mask and the stripe mask in which the windows are distributed in a zigzag pattern can be clearly distinguished from each other in shape and size. The ELO mask distributes many small windows having a diameter of 1 μm to 2 μm at a pitch of about 2 to 6 μm. The stripe mask has a width s of about 10 μm to 300 μm and a pitch p of about 20 μm to 2000 μm. For example, the stripe mask has a width s of 50 μm and a rough mask such that p = 500 μm.

  In the dot-type and stripe-type facet growth methods, the dislocations are concentrated in the crystal defect gathering region H on the mask and surrounded by the crystal grain boundaries K, K, so the dislocations are not re-discrete. Z and Y adjacent to H become a single crystal with low dislocations. The part may be a part through which the current of the device passes.

  Since the GaN crystal has a cleavage plane in the {1-100} direction, a laser resonator mirror can be formed by natural cleavage. Since oxygen is doped to form an n-type, an electric current passes and an n-electrode can be formed on the bottom surface. In that respect, it is superior to sapphire substrates.

  ELO has a small exposed area and a high dislocation density above it, and a wide covering area and a low dislocation. On the other hand, the striped facet method has a wide exposed area and a low dislocation, and a narrow covering area. High density dislocations.

  The growth conditions in Examples (all HVPE methods) of Patent Document 10 are as follows.

The growth temperature Tq, NH ₃ partial pressure P _NH3 , HCl partial pressure P _HCl , and _5/3 group ratio b are shown in this order.
1050 ° C 30 kPa 2 kPa 15 times
1030 ° C 30 kPa 2.5 kPa 12 times
1050 ° C 30 kPa 2 kPa 15 times
1010 ° C 20 kPa 2.5 kPa 8 times
1030 ° C 25kPa 2kPa 12.5 times
1030 ° C 25 kPa 2.5 kPa 10 times
The substrate temperature of Patent Document 10 is 1010 ° C. to 1050 ° C., and the 5/3 group ratio b is 8 to 15 times. The six points with the numeral “10” in the center part of the lower half of FIG.

Patent Document 11 discloses a MOCVD method using H ₂ , TMG, and ammonia as source gases and (C ₅ H ₅ ) ₂ Fe as a dopant on a sapphire (0001) substrate, or H ₂ , HCl, Ga melt, and ammonia. A method has been proposed in which an iron-doped GaN substrate is obtained by growing an iron-doped GaN crystal by the HVPE method using (C ₅ H ₅ ) ₂ Fe as a dopant. Patent Document 11 tries to make a semi-insulating substrate by doping iron.

Example of Patent Document 11 (MOCVD
The growth conditions in the method are as follows.

The growth temperature Tq, NH ₃ partial pressure P _NH3 , TMG partial pressure P _TMG , and _5/3 group ratio b are shown in this order.
1000 ° C 15 kPa 0.3 kPa 50 times
This is indicated by a black dot and a white circle at a coordinate point of 50.times.

The growth conditions in the example (HVPE method) of Patent Document 11 are as follows.

The growth temperature Tq, NH ₃ partial pressure P _NH3 , HCl partial pressure P _GaCl , and _5/3 group ratio b are shown in this order.
1000 ° C 15 kPa 0.3 kPa 50 times
This is indicated by a black circle at a central point of 1000 ° C. in FIG.

International Publication WO99 / 23693 (International Application PCT / JP98 / 04908)

Japanese Patent No. 3788037 (Japanese Patent Application No. 10-171276, Japanese Patent Laid-Open No. 2000-012900)

Japanese Patent No. 3788041 (Japanese Patent Application No. 10-183446, Japanese Patent Laid-Open No. 2000-022212)

International Publication WO 98/47170 (International Application PCT / JP98 / 01640)

EPC Publication EP0942459 A1 (EPC Application No. 9891274.8)

Japanese Patent No. 3788104 (Japanese Patent Application Laid-Open No. 2000-044400, Japanese Patent Application No. 11-144151 / Claim of priority Japanese Patent Application No. 10-147716)

Japanese Patent No. 3826825 (Japanese Patent Application Laid-Open No. 2002-373864, Japanese Patent Application No. 2002-103723 / claim of priority Japanese Patent Application No. 2001-113873)

JP 2001-102307 (Japanese Patent Application No. 11-273882)

Japanese Patent No. 3864870 (Japanese Patent Application Laid-Open No. 2003-165799, Japanese Patent Application No. 2002-230925 / claim of priority Japanese Patent Application No. 2001-284323)

Patent No. 3801125 (Japanese Patent Application Laid-Open No. 2003-183100, Japanese Patent Application No. 2002-269387 / Priority Claim Japanese Patent Application No. 2001-311018)

JP-A-2005-306723 (Japanese Patent Application No. 2005-075734 / Priority Claim Japanese Patent Application No. 2004-085372)

  What has been described so far are the blue light emitting diodes, n-type GaN substrates used as semiconductor laser substrates, and semi-insulating (SI) GaN substrates used as FET substrates. Although an AlInGaN substrate containing a little Al or In has been attempted, it is for use as a substrate of a light emitting device. It is n-type, has high conductivity, and can pass a high-density current. The dopant may be silicon (Si) or oxygen (O).

  In the case of a light-emitting element, since a high-density current flows through the substrate, there is a risk that deterioration will proceed from dislocation. A low dislocation density is desired in terms of suppressing deterioration. But that is not all.

  If the substrate has a high dislocation density, it causes a leakage current, which is not preferable. Since multiple layers of GaN, InGaN, and AlGaN thin films having a regular lattice structure are formed on the substrate, fewer dislocations are better. Since it is a board | substrate for manufacturing a semiconductor element on it, it is good that there are few curvatures and there are few cracks. Therefore, when a conductive substrate is used, it is strongly desired that the substrate has high conductivity, low warpage, low dislocation density, and few cracks.

All of the GaN substrates mentioned in the prior art (Patent Documents 1 to 10) are n-type with low resistivity.

Patent Document 1 says that 0.005 to 0.08 Ωcm, and Patent Document 2 says 0.0035 to 0.0083 Ωcm. Patent Document 3 states that the GaN substrate is 0.01 to 0.017 Ωcm.

Since Patent Documents 1 to 3 do not describe that an n-type dopant has been added, it is considered that Group 5 vacancies have created a donor level or that an n-type dopant element contained in the source gas has entered.

  Patent Document 4 does not specifically describe the resistivity. This intends to make a low resistance n-type GaN substrate with Si as a dopant. Therefore, it is estimated that the resistivity will be lower than those of Patent Documents 1 to 3. From these descriptions, it is considered that the upper limit of the specific resistance of the conventional GaN crystal is 0.08 Ωcm, and the lower limit is about 0.005 Ωcm.

Dislocations cannot be reduced sufficiently by the ELO method. The facet growth method proposed by Patent Documents 8 and 9 has an effect of reducing the dislocation density. In order to make conductive GaN, a method of doping oxygen and a method of doping Si are currently known. In the case of oxygen doping as in Patent Documents 6 and 7, water or oxygen may be mixed in the source gas. These are safe substances. In the case of Si doping as in Patent Documents 4 and 5, it is necessary to supply silane (SiH ₄ ) gas. Silane gas is a dangerous gas and is not desirable to use in large quantities. Is there any surface dependence on the absorption of SiH ₄ gas? Is n’t it? That's not clear. In the case of doping silicon, there has been no research on whether there is doping anisotropy in the C-plane, M-plane, A-plane, or generally the F-plane (the facet plane is abbreviated in this way). If silicon has the same plane orientation dependency as oxygen, the n-type impurity doping amount cannot be averaged. However, if the surface dependence of Si and oxygen (O) is different, the specific resistivity may be complementarily made uniform.

  The facet growth method is a useful method for reducing the dislocation density. By collecting the dislocations in the closed defect gathering region on the mask, the dislocation density in other portions can be reduced. Moreover, since the surface has a concavo-convex structure, it seems that there is little warpage and the occurrence rate of cracks is small.

  However, the facet growth method has its drawbacks. One is that when oxygen is doped, oxygen absorption is anisotropic. When an oxygen-doped n-type crystal is formed using the facet growth method, the doping efficiency has a large plane orientation dependency. Patent Document 7 states that the oxygen doping efficiency is lowest on the C-plane, and oxygen is absorbed 50 times or more at the facet. When the facet growth method is performed, a portion that grows on the facet and a portion that grows on the C-plane are mixed. On the C plane, oxygen does not enter so much, so the oxygen concentration becomes low. In the facet, oxygen tends to enter 50 times or more compared to the C-plane, so the oxygen concentration becomes high. Since the facet grown crystal also has a C plane in part, the oxygen concentration becomes uneven in the crystal. In that case, when a device is formed on the substrate as a substrate, the conductivity is greatly different for each element.

  When the C-plane growth is performed instead of facet growth, oxygen does not enter and the specific resistance increases. Crystals made by the C-plane growth method that grows while maintaining a flat surface have an impression that cracks are easy to break and are easy to break, and those made by the facet growth method have the impression that they are harder to crack and harder. is there. We want to make an n-type substrate with few cracks, little warpage, and uniform resistivity. An object of the present invention is to provide an n-type GaN substrate having a small crack generation rate, a small warpage, and a uniform resistivity.

  In the method for producing an n-type nitride semiconductor substrate according to the present invention, a dot mask or a stripe mask is attached to a base substrate, the substrate temperature is set to 1040 ° C. to 1150 ° C., and the ratio of the Group 5 and Group 3 gas raw materials is further increased by HVPE. While supplying ammonia gas, Group 3 gas, Si-based compound gas, and oxygen (O) so that b is 1 to 10, oxygen and Si are formed on the facet surface on the base substrate with a mask, and a C-plane growth region. Mainly grows a nitride semiconductor crystal thickly while doping Si, removes the underlying substrate, has a thickness of 100 μm or more, has little warpage, has a low crack generation rate, has a low specific resistance, and has a low specific resistance. A silicon and oxygen-doped conductive nitride semiconductor crystal substrate with a small variation in characteristics is obtained.

  As in the prior art, two types of dopants are used instead of one type of dopant, and different dopants are mainly added on the facet and the C plane so that the specific resistance is made uniform in a complementary manner.

  There is no example of GaN growth so far that the 5/3 group ratio b is as low as 1 to 10 and the temperature is as high as 1040 ° C. to 1150 ° C. As shown in FIG. 22, the 5/3 group ratio b is larger than 10 in many GaN growth methods (parts of Patent Documents 1, 4, 7, 8, and 10, 11). There is also a document (a part of Patent Documents 2, 3, 9 and a part of 10) that causes the 5/3 group ratio b to be smaller than 10, but this is a low temperature of less than 1040 ° C.

  In the 5/3 group ratio b = 1 to 10, in the temperature range of 1040 ° C. to 1070 ° C., facets strongly appear and the surface becomes a strongly inclined slope. This crystal having a strong uneven surface is called type II. This is shown in FIG. Since the covering portions M arranged at a rough pitch are attached to the base substrate U and facet growth is performed, the upper portion of the covering portion M becomes a crystal defect gathering region H, and on both sides thereof, facet F, F is followed by low defect single crystal regions Z, Z Will occur. Facets F, F persist until the end of growth. The entire surface may become facet F. In some cases, a part is shaved (broken line) to become a C-plane, and a subsequent portion becomes a C-plane growth region Y. Depending on the proportion of facets, the C-plane growth region Y may not exist in the middle of Z and Z, and the C-plane growth region Y may exist in part.

Since a wide mask is periodically provided on the base substrate U and a nitride semiconductor is grown thereon, the present invention employs the facet growth method. Therefore, many facets rising from the covering portion M are generated. It grows facet in the process as shown in FIGS. A crystal defect assembly region H is formed on the covering portion M, and a low defect single crystal region Z and a C-plane growth region Y are formed in the exposed portion E. A low-defect single crystal region Z is generated under the facet, and a C-plane growth region Y is generated under the C-plane. In the case of the facet type II, the surface grows with the facet predominating. In the case of type I having a flat surface, the temperature is high, so that the C surface eventually dominates and finally the flat C surface occupies the entire surface. In any case, oxygen is mainly taken in because facet growth occurs partway through.

  The coating part width (diameter) is represented by s, the coating part interval is represented by w, and the coating part pitch is represented by p. s = 10 μm to 100 μm, w = 250 μm to 10000 μm. The covering portion is formed on the base substrate with regularity. If there is regularity, s, w, and p can be defined. A typical one includes a set having a cover (dot type, FIG. 26) set of isolated points and a set having a parallel strip-like cover (stripe type, FIG. 25). Other regular patterns may be used.

  In the 5/3 group ratio b = 1 to 10 and in the higher temperature range of 1090 ° C. to 1150 ° C., the surface finally becomes a flat C plane. This crystal with less unevenness is referred to herein as type I. FIG. 21 shows a type I crystal. Even in the case of the I type, crystal growth is performed using a mask, so the facet growth is performed halfway. Near the end of growth, it becomes C-plane growth. Therefore, a crystal defect gathering region H is formed on the mask M, low defect single crystal regions Z are formed on both sides thereof, and a C-plane growth region Y is formed in the middle of the mask. Although the upper surface is a C-plane, it grows after the covering portion having a large pitch is attached to the base substrate, so that facet growth occurs. C-plane growth occurs after the crystals continue to grow and become sufficiently thick. Therefore, the type I of the present invention is different from the conventional C-plane growth method. The coating part width (diameter) is represented by s, the coating part interval is represented by w, and the coating part pitch is represented by p. s = 10 μm to 100 μm, w = 250 μm to 10000 μm. The covering portion is formed on the base substrate with regularity. If there is regularity, s, w, and p can be defined. A typical one includes a set having a cover (dot type, FIG. 26) set of isolated points and a set having a parallel strip-like cover (stripe type, FIG. 25). Other regular patterns may be used.

  At 5/3 group ratio b = 1-10 and at a medium temperature of 1070 ° C. to 1090 ° C., a mixed type in which the middle of the mountain is shaved is obtained. FIG. 24 shows a mixed crystal cross-sectional view. Since crystal growth is performed after the covering portion M having a large pitch is attached to the base substrate U, facet growth is performed. Immediately above the covering portion M is a crystal defect gathering region H. On the both-side exposed portion E, the portion following the facet F becomes a low defect single crystal region Z. Below the C plane sandwiched between Z and Z is C plane growth. C-plane growth becomes dominant after crystal growth is sufficiently thick. The C-plane grown portion becomes a C-plane growth region Y. Facet F remains on the surface until the end. The coating part width (diameter) is represented by s, the coating part interval is represented by w, and the coating part pitch is represented by p. s = 10 μm to 100 μm, w = 250 μm to 10000 μm. The covering portion is formed on the base substrate with regularity. If there is regularity, s, w, and p can be defined. A typical one includes a set having a cover (dot type, FIG. 26) set of isolated points and a set having a parallel strip-like cover (stripe type, FIG. 25). Other regular patterns may be used.

  In either case, the surface is finally ground and polished to form a flat mirror surface. Therefore, the Yamatani structure no longer exists if it becomes a mirror wafer. This is the structure immediately after the previous crystal growth. The mirror wafer has a thickness of 100 μm or more. This is because it can stand on its own. It may be thicker. It may be 300 to 10,000 μm. If it is thick, the wafer is cut in parallel to form a plurality of wafers. The original HZYZHZYZ... Structure remains as a wafer and has anisotropy in the lateral direction. Since they are transparent, they cannot be seen with the naked eye, but can be seen with CL (cathode luminescence) or a fluorescence microscope.

  Another feature of the present invention is the double doping of silicon and oxygen. In the II type and the mixed type, the C surface and the F surface (facet) are mixed on the surface. Even in the I type, the C surface and the F surface coexist halfway. Oxygen has a plane orientation dependency in which a large amount is doped in the F plane and a small amount is doped in the C plane. If silicon has the opposite plane orientation dependence of doping on the C-plane and less on the F-plane, the amount of n-type dopants on the C-plane and F-plane is complemented by double doping with silicon and oxygen. Can be. But even in that case, when oxygen and silicon are double doped, can the two dopants interfere with each other (interference effect)? Even if oxygen and silicon emit n-type carriers independently without interference, the activation rates are different, so the amounts of oxygen and silicon required are different. Is it possible to handle oxygen doping and silicon doping one-on-one (superior or inferior)? In addition, the ratio of the C plane and F plane (C plane / F plane ratio) differs depending on the crystal growth method. This is not only different in ratio as a whole, but also in the growth direction (height direction). If the ratio of the C plane and the F plane is different, the specific resistance as a whole should be different. Various things must be clarified to enable a design to obtain a specific resistivity by double doping. The double doping of n-type dopants is not described in Patent Documents 1 to 11 cited so far. In addition, there was no literature of double dope in the place where this inventor investigated.

  A number of experiments by the inventor have shown that silicon does not appear to be plane orientation dependent. In other words, silicon seems to be doped to the same extent on the C and F planes. Oxygen absorbs significantly differently on the C and F planes. It seems to be larger than the value of 50 times pointed out by US Pat.

  Thus, in facet growth in which the C plane and F plane coexist, when a nitride semiconductor crystal is grown in an atmosphere containing both silicon and oxygen, the n-type dopant concentration is averaged between the C plane and the F plane, and the local resistivity is increased. Can be reduced. As described above, in the present invention, the 5/3 group ratio b is set to a low value of 1 to 10, and the substrate temperature is set to a high temperature of 1040 ° C. to 1150 ° C. If the facet covers the entire surface even during growth, as shown in type II (FIG. 20), oxygen is the main dopant. Oxygen can be introduced into the atmosphere by including water or oxygen gas in ammonia, hydrogen, or HCl gas. Since there is a slight C-plane, it is Si-doped to give n-type carriers.

  Even if the surface is covered with the C-plane as in the case of type I (FIG. 21), it grows with facets up to the middle, so oxygen is actively doped. As the end of growth is approached, the C surface becomes dominant and oxygen becomes difficult to enter. Instead, dope silicon.

In the mixed type (FIG. 24), the facet growth is continued to the end as in the case of the type II, so that oxygen sufficiently enters through the facet. The C plane is doped with silicon.
The underlying substrate may be any substrate as long as the nitride semiconductor grows in the c-axis direction. (111) plane GaAs wafers, C plane sapphire wafers, C plane SiC wafers, C plane GaN wafers, and the like can be used. Masks, etc. _SiO 2, SiN, AlN, a metal film.

FIG. 19 shows a schematic longitudinal sectional view of the HVPE furnace. A heater 3 is provided outside the vertically long reactor 2. The heater 3 extends in the vertical direction and is divided into several parts, and can generate an arbitrary temperature distribution in the vertical direction. The reactor 2 has a hot wall. A Ga reservoir 4 in which Ga melt is stored is provided in the upper part of the reaction furnace 2. Below the reaction furnace 2 is a susceptor 5 supported on a rotary shaft that can be rotated and raised. A base substrate 6 is placed on the susceptor 5. The first source gas supply pipe 7 supplies hydrogen (H ₂ ) and hydrogen chloride (HCl) gas to the Ga reservoir 4. HCl and Ga react to form GaCl gas. This moves downward. The second source gas supply pipe 8 allows hydrogen (H ₂ ) and ammonia (NH ₃ ) gas to flow above the base substrate 6. GaCl and NH ₃ react to form GaN. The third source gas supply pipe 10 supplies a gas mixture of silicon (Si) (for example, silane SiH ₄ ) and a carrier gas (H ₂ ) into the reaction furnace. In order to add oxygen, water or oxygen gas is supplied to the raw material (H ₂ + HCl) of the first raw material gas supply pipe 7, the raw material (NH ₃ + H ₂ ) of the second raw material gas supply pipe 8, or the third raw material gas supply pipe 10. The raw material (SiH ₄ + H ₂ ) is mixed and supplied. The synthesized GaN is doubly doped with Si and O. After the reaction, exhaust gas and unreacted gas are discharged from the gas discharge pipe 9.

Si uses Si chloride, fluoride or hydride (SiH ₄ ) as a raw material. Since these are gaseous, they are blown into the reactor as gas from the upper gas flow path. These are thermally decomposed and taken into the crystal. Within the crystal, oxygen and silicon coexist as n-type dopants.

  The nitride semiconductor substrate of the present invention thus produced has a crack occurrence rate K of 22% or less. The lower limit of the crack occurrence rate K is about 1% (0.01 ≦ K ≦ 0.22). Speaking of type II only, the crack generation rate is 18% or less (K ≦ 0.18 (type II)). Patent Documents 2 and 3 describe that all GaN free-standing crystals having a flat surface are broken by polishing, and all GaN substrates of Patent Documents 2 and 3 having a flat surface have a crack occurrence rate K of 100%. That's what it means.

The curvature radius U of the curvature of the nitride semiconductor substrate of the present invention is 3.5 m to 7 m (3.5 m ≦ U ≦ 7 m). When the surface is limited to type II having faceted irregularities, 4.2 m ≦ U ≦ 7 m. In Patent Documents 2 and 3 based on the ELO method, the unpolished flat surface crystal has a curvature radius of 0.054 m to 0.167 m. This is extremely warped.
The curvature radius of the unpolished rough surface crystal is assumed to be 4 sheets of 1 m to 2.6 m and 1 sheet of 10 m. Since the warpage increases when polished, the warpage increases to 3.4 m when a single sample having a radius of curvature of 10 m and not polished is also polished. That is, the curvature radius of the rough surface substrate in Patent Documents 2 and 3 is U ≦ 3.4 m. The crack occurrence rate of this sample of Patent Documents 2 and 3 is not described. The substrate temperature is 1020 ° C., which is lower than the substrate temperature of the present invention. C-face growth, not facet growth. It states that the specific resistance is 0.05 Ωcm. In Patent Documents 2 and 3, since there is no description of the dopant, it is unknown. Although there are literatures that express the warp with the radius of curvature U, there are also cases where the warp is expressed with the height h of the center of the wafer placed on a flat surface. When the diameter of the wafer is D and the center height of the wafer is h, it can be converted because there is a relationship U = D ² / 8h. The curvature radius U of the present invention is 3.5 m to 7 m when h = 89 μm to 45 μm for a 2 inch diameter (50 mm).

The silicon concentration in the nitride semiconductor substrate of the present invention is 5 × 10 ¹⁹ cm ⁻³ ≧ Si ≧ 1 × 10 ¹⁷ cm ⁻³ . The oxygen concentration is 1 × 10 ¹⁹ cm ⁻³ ≧ O ≧ 1 × 10 ¹⁵ cm ⁻³ . However, O = 1 × 10 ¹⁵ cm ⁻³ is an oxygen detection limit and may actually be much smaller. This will be described later.

The resistivity r of the nitride semiconductor substrate of the present invention is 1 × 10 ⁻² Ωcm or less. A low thing of 1.5-2 * 10 < ^-3 > (omega | ohm) cm is also obtained. That is, the specific resistance r of the crystal obtained in the present invention is 0.0015 Ωcm ≦ r ≦ 0.01 Ωcm. It exceeds the specific resistance 0.005 Ωcm ≦ r ≦ 0.08 Ωcm of Patent Document 1. As an n-type substrate, it is possible to obtain an excellent nitride semiconductor crystal with a low resistance and a low crack generation rate and with little warpage.

_Masks, etc. SiO 2, SiON, SiN, AlN , Al 2 O 3. The mask may be a periodic pattern having a narrow covering portion and a wide exposed portion. Here, the stripe coating (parallel strip shape) and the dot coating (isolated staggered distribution) are described, but a coating portion having other periodicity may be used. In the case of a stripe mask, the mask has a covering portion width s of 10 μm to 100 μm. The space | interval w of a coating part shall be 250 micrometers-10000 micrometers. The pitch p is p = s + w. The pitch is p = 260 μm to 10100 μm.

In the case of a dot mask, the covering portion diameter s is 10 μm to 100 μm. The space | interval of a coating part shall be w = 250 micrometers-10000 micrometers. Pitch p is 260 μm to 10100
μm.

When the 5/3 group ratio b is 1 to 10 and the substrate temperature is 1040 ° C. to 1080 ° C., a chevron crystal (type II) having a facet surface that is low at the mask position and high at the exposed portion grows (FIG. 20). . It is facet growth because it is low in the coating and high in the exposed part. Facets (simply called F-plane) can absorb oxygen vigorously. The facets are both doped with oxygen and silicon. Facet growth continues to cycle. A crystal defect gathering region H is formed on the mask, and a low defect single crystal region Z is formed immediately below the facet F near the mask at the exposed portion E. The oxygen supply amount is O (t) and the Si supply amount is Si (t). These may be constant during growth. O (t) = C ₂ and Si (t) = C ₁ (C ₁ and C ₂ are constants).

FIG. 20 shows an ideal form (type II) composed only of mountain shapes to emphasize the comparison with FIG. The ideal form is a repetition of ZHZHZH. This is realized only in a special case with a stripe mask. This is not the case with dot masks due to geometric constraints. ZHZYZHZYZH ... is repeated. In both the dot mask and the stripe mask, a C plane is actually formed at the middle position of the mask (indicated by a broken line), and a C plane growth region Y is often formed below the C plane. Since oxygen hardly enters the C side, silicon enters instead. Si is necessary for C-plane doping. In the initial stage of growth, the influence of the covering portion M and the exposed portion E is strong, and the facet F is overwhelmingly dominant. At the end of growth, the influence of the distinction between the covering portion and the exposed portion is weakened, and a part of the C-plane is likely to appear. In consideration of such a situation, the supply of Si-containing gas (for example, SiH ₄ gas) may be initially set to 0 or slightly, and gradually increased to increase the supply of Si according to the appearance probability of the C plane. For example, the supply amount Si (t) of the Si-containing gas is set to Si (t) = C ₃ t + C ₄ t ² +... (C ₃ and C ₄ are positive constants, and t is time). As a result, the donor concentration can be further averaged in the thickness direction.

The type II holding the facet (F surface) to the end is most desirable because of low crack generation rate, low warpage, robustness, low dislocation density, and ease of oxygen doping. However, the C-plane may appear somewhere during the growth. If oxygen doping alone is used, the donor density (n-type dopant) in that portion is lowered, but since the present invention also doped Si, the C plane also has a considerable donor density. The donor density can be made uniform by doping the F plane with oxygen + Si and the C plane with Si. Moreover, most of the donor is oxygen and the amount of Si doping is small. There is no need to use a lot of dangerous SiH ₄ gas, and safety is high. A type II crystal is a repetition of ZHZYZHZYZH. Tension can be alleviated because of the structure in which different things such as H and Z or H, Z and Y are mixed. This reduces the internal stress and reduces the crack generation rate.

  When the substrate temperature is higher, from 1080 ° C. to 1150 ° C., crystals having a uniform height (type I) grow (FIG. 21). In the I type, the surface is a substantially flat C plane. Actually, the upper part of the mask M may be slightly depressed. Si is introduced as a donor into the C plane. But that doesn't mean the whole donor is Si. Oxygen is important. A significant amount of donor is oxygen. Even in the I type, the growth starts from the exposed part E, and a facet is created to grow. A crystal defect gathering region H is formed on the covering portion M, and a low defect single crystal region Z and a C-plane growth region Y are formed on the exposed portion. Since the temperature is high, it approaches C-plane growth as it approaches the end of growth. A crystal defect gathering region H is formed on the mask, and a low defect single crystal region Z and a C-plane growth region Y are mixed on the exposed portion. The surface is a C plane. Stress can be relieved because of the structure (HZYZHZYZ...) In which different structures alternate.

  Type I initially grows faceted, and the crystal has a lot of facets, so it can absorb a lot of oxygen. Since Si has no selectivity, it also enters the F plane. The inside of the crystal is sufficiently doped with oxygen. Oxygen and Si are simultaneously doped through the F plane. However, as the end of growth is approached, the facet decreases and approaches C-plane growth. Since facet F decreases, oxygen is not taken in, but Si is absorbed because there are many C faces. In the I type, the effect of Si doping becomes remarkable at the end of growth. Si acts as a complementary dopant. The surface is rich in Si, and oxygen (O) is rich inside.

Si may be introduced from the beginning as a dopant, and the supply amount may be constant (Si (t) = C ₁ ). In that case, oxygen and Si are simultaneously doped into the F plane even in the initial facet growth. As the end of growth is approached, the C-plane dominates and only Si is doped. That is, Si is always absorbed quantitatively, but oxygen absorption decreases. Then, the donor density changes in the thickness direction, and the donor density is lower on the surface. Then, the specific resistance of the surface is greatly increased.

At first, facet growth is performed, and C plane growth is approached as the end is approached, so time variation may be given to the supply of Si. The Si-containing gas (for example, SiH ₄ gas) is not initially supplied, but the supply amount is gradually increased, and the Si-containing gas is maximized as the end of the process is approached. Si (t) = C ₃ t + C ₄ t ² +... (C ₃ and C ₄ are positive constants, and t is time). Then, oxygen and Si are taken in through the F plane in the initial and middle F planes, and Si is taken in through the C plane in the final stage. The concentration in the thickness direction of the donor (n-type dopant) can be made uniform.

Since resistance measurement is performed between two points on the surface, the influence of Si doping is strong. However, when a device is formed on the n-type substrate, the current flows up and down, so that the oxygen concentration is strong. Since the measurement is performed between two distant points, the specific resistance value is obtained by averaging local fluctuations in the horizontal direction. Still, the specific resistance in the vertical direction is different from the specific resistance in the lateral direction. When the resistivity is measured on the surface, both the effects of oxygen doping and Si doping appear in the case of type II. In the case of a C-plane I-type surface, the Si-doped portion contributes greatly. Therefore, the I type has high conductivity (low specific resistance) almost in proportion to the Si doping amount.
When there is little Si dope, type I has a high surface resistivity. However, it is only the surface and the inside is doped with oxygen, so the conductivity in the vertical direction is high.
Since the I type also has an HZYZHZYZ... Structure inside, the internal stress can be relaxed. The crack generation rate can be lowered.
In order to make type I, it is better that the 5/3 group ratio b is lower at a higher temperature. The 5/3 group ratio b is set to 1 to 10 at a high temperature of 1080 to 1150 ° C. Furthermore, when the temperature is set to 1090 ° C. to 1150 ° C. and the 5/3 group ratio b is set to about 1 to 5, it can be more surely made into the I type.

At 5/3 group ratio b = 1 to 10 and a substrate temperature close to 1080 ° C. (1070 ° C. to 1090 ° C.), a crystal having a trapezoidal apex in which type I and type II are mixed is formed (FIG. 24). This grows facet initially. Crystal growth starts on the exposed portion E, facets are formed from the end of the exposed portion E, and the growth start is delayed on the covering portion. A low-defect single crystal region Z and a C-plane growth region Y are formed in the exposed portion E. A crystal defect gathering region H is formed on the covering portion M. Since facet growth occurs, oxygen is absorbed by facet F (F plane). Si also enters facet F. Both F and Si are doped in parallel with Si and oxygen. A crystal defect gathering region H is formed on the covering portion M and changes to C-plane growth approaching the end of growth, but facets remain until the end. Si enters the C side. The dopant distribution is made more uniform. It has a structure of HZYZHZYZ... And can reduce internal stress and lower the crack generation rate.

  Three cross-sectional views (FIGS. 20, 21, and 24) of type II, type I, and mixed type are shown. However, a phase transition in which the cross-sectional shape suddenly changes at a certain temperature does not occur. / The cross-sectional shape continuously changes depending on the group 3 ratio b. An ideal flat mold as shown in FIG. 21 can be obtained at a temperature of 1090 to 1150 ° C. and a group 5/3 ratio b1 to b3. As the temperature decreases, the flat shape in FIG. 21 changes to the mountain shape in FIG. 20 as the 5/3 group ratio b increases.

The substrate temperature of 1050 ° C. to 1150 ° C. is the higher growth temperature of the nitride semiconductor vapor phase growth method. I-type growth means that if the temperature is raised, even a large mask can be grown with a flat surface in the end.

It can be said that the 5/3 group ratio b is 1 to 10 is an extremely small limit in the vapor phase growth method of a nitride semiconductor. The idea of the present invention is to grow a Si / O-doped nitride semiconductor with a low 5/3 group ratio b and a high growth temperature.

Since Si and oxygen are doubly doped, Si enters the C plane and forms a highly uniform donor concentration distribution together with oxygen on the F plane, and a conductive nitride semiconductor substrate having a specific resistance r of 10 ⁻² Ωcm or less. Obtainable. The lower limit of the specific resistance r can be pushed down to 0.0015 Ωcm. The specific resistance range of the substrate of the present invention is 0.0015 Ωcm ≦ r ≦ 0.01 Ωcm.

  Since a mask having a large repetitive pitch is formed on the base substrate and crystal is grown thereon, structures having different structures such as a crystal defect gathering region H, a low defect single crystal region Z, and a C-plane growth region Y can be formed. That is, a structure in which different phases of ZYZHZYZ. Since it relieves internal stress, a crystal with less warpage U can be obtained. The curvature radius of warpage can be 3.5 m ≦ U ≦ 8 m.

  Since a mask having a large repetitive pitch is formed on the base substrate and crystal is grown thereon, structures having different structures such as a crystal defect gathering region H, a low defect single crystal region Z, and a C-plane growth region Y can be formed. Since it relieves internal stress, a substrate with less cracking is obtained. The crack occurrence rate K can be 1% ≦ K ≦ 22%.

  In the facet growth method proposed in Patent Documents 8, 9, and 10, dislocations at peripheral portions (Z, Y) are provided by providing a mask with a wide exposed portion on a base substrate and concentrating crystal defects on the mask. Has the effect of reducing They were intended to reduce dislocations.

  When growing a crystal for an n-type substrate, a high-density current flows through the n-type substrate, so that dislocations may proliferate. In order to avoid this, it is desirable that the dislocation density is low. A direct advantage of facet growth is that it reduces the dislocation density. But that is not the only advantage of the faceted growth method.

  In the facet growth methods of Patent Documents 8, 9, and 10, portions H, Z, and Y having different structures are generated in the crystal, which relieves stress. Therefore, it has been found that there is an effect of reducing warpage and suppressing the occurrence of cracks. Since the C-plane growth methods of Patent Documents 1, 2, and 3 only have the same crystal structure, there is not much effect of stress relaxation. A flat surface crystal cannot be polished with a curvature radius of several tens of centimeters and a crack generation rate of 100%. Some rough crystals have a warp of about 1 m and can be polished, but the crack generation rate is high and it is difficult to use.

  Therefore, the present invention also uses the facet growth method when making an n-type impurity-doped GaN crystal. Some facet growth methods do not have a mask as in Patent Document 8, but as in Patent Documents 9 and 10, a facet is forcibly created by attaching a mask to the base substrate and the facet is formed from the edge of the mask. Some of them can specify the position where the image can be recorded in advance. This always creates facets, so if it is maintained until the end so as not to embed the facets, dislocations are concentrated on the mask to form crystal defect gathering regions H on the mask, and the dislocation density in the other parts is set. Can be reduced.

  When facet growth is performed by a method using a mask with a large exposed portion having a large period as shown in Patent Documents 9 and 10, a crystal defect aggregate region H in which defects are concentrated, and a low defect single crystal region Z and C plane growth with few defects A structure in which the region Y alternates can be formed, and internal stress can be relaxed.

It has been found that the facet growth method with a mask with a large exposed part having a large period has excellent effects of reducing dislocation density, reducing warpage, and preventing cracks.
In order to manufacture a highly conductive GaN crystal, an n-type impurity must be doped at a high concentration. When a single crystal structure is doped with an impurity at a high concentration, a strong internal stress is generated, the warpage is increased, the element is easily broken, and dislocations are increased. The facet growth method will be able to reduce the internal stress caused by the addition of high-concentration impurities by creating a composite structure of HZYZH ... structure.

  It is expected that the facet growth method will also be useful when making n-type conductive crystals. However, from the viewpoint of producing an n-type highly conductive crystal, the facet growth method has an unexpected defect. Patent Document 6 revealed for the first time that oxygen forms a donor in GaN to form an n-type crystal. This is because it has been found that safe water can be used to dope n-type impurities (O) and the activation rate is close to 100%. However, Patent Document 7 has found that there is a strong plane orientation dependency on oxygen doping. It is a plane orientation preference that oxygen enters through the facet, but almost no oxygen enters the C plane. When an oxygen-doped n-type crystal is produced by the facet growth method, not all facet surfaces (F surfaces) but C surfaces are mixed. Under the F surface is high conductivity, and under the C surface is high resistance. When facet growth is performed, a large local fluctuation occurs in the oxygen doping amount.

When different types of base substrates such as GaAs and sapphire are used, the growth is performed in the c-axis direction. The region below the C plane is referred to as a single crystal low dislocation residual region Y or a C plane growth region Y, which does not contain oxygen and has a high resistance. When the HZYZHZYZH... Structure is made by the facet growth method, H and Z contain oxygen and become highly conductive, and Y becomes oxygen and no resistance. The resistivity varies locally and periodically.
This is a problem. Moreover, this problem occurs for the first time because oxygen is used as an n-type impurity and the facet growth method is employed. Si is exclusively used as the n-type impurity of the GaN thin film. This is a problem that does not occur in the usual method of growing C-plane using Si as an n-type dopant.

  Therefore, in the present invention, oxygen and silicon are simultaneously doped while facet growing. If silicon has a C-plane preference, it should be able to counteract with the F-plane preference of oxygen and skillfully form a uniform concentration donor distribution. However, according to many experiments by the present inventors, it has been found that silicon does not depend on the plane orientation and enters the C plane and the F plane in the same way. Then, when silicon (Si) and oxygen (O) are simultaneously doped, Si and O enter the F surface and Si enters the C surface, and n-type impurities can be added from all surfaces. In the case of a C-plane underlying substrate (sapphire, GaN) or (111) GaAs substrate, if facet growth is performed, an HZYZHZ... Structure is formed, but Y also contains Si and has a low resistance. The high resistance region will be erased. Since the high resistance region is eliminated, the local fluctuation of the conductivity is reduced and the substrate can be used as an n-type highly conductive substrate.

  The present invention has two characteristics: oxygen and silicon double doping and facet growth. Since facet growth has been described in detail, doping will be described. The double doping of oxygen and silicon in a nitride semiconductor is unprecedented. I could not find the literature.

  A certain element is different from being n-type with respect to GaN or nitride semiconductor and being usable as an n-type dopant. There are some n-type impurities such as carbon in addition to oxygen and silicon. However, they are not always available as n-type dopants. If silicon and oxygen coexist, they may interfere with each other in the crystal and suppress each other. Oxygen may not make a shallow donor due to the coexistence of silicon. Conversely, silicon may not be able to form a donor due to the presence of oxygen. Even if the donor level is achieved, silicon may capture n-type carriers released by oxygen. In other words, there may be checks by interaction. If so, the conductivity cannot be increased by doping two kinds of n-type impurities.

  There is no interference between the two types of n-type impurities and they are independent, and even if each emits one n-type carrier, the activation rate will be different, so the effect should not be the same. If the electron charge is e, the mobility of n-type carriers is μ, and the concentration of n-type carriers (free electrons) is n, the conductivity σ can be written as σ = nμe. The activation rates of oxygen and silicon are Mo and Ms. When the oxygen concentration is [O] and the silicon concentration is [Si], since silicon and oxygen are independent, n = Mo [O] + Ms [Si], conductivity σ = μe (Mo [O] + Ms [Si] ]) Can be written symbolically. When expressed by a specific resistance r, r = 1 / σ = 1 / μe (Mo [O] + Ms [Si]). In other words, if the oxygen concentration [O], the silicon concentration [Si], and the specific resistance r are in the above relationship, Si and O do not interfere with each other, do not cancel each other, do not check, and are independent from each other. It is.

  The oxygen and silicon concentrations are measured at a certain point on the C-plane and F-plane of the sample by SIMS (Secondary Ion Mass Spectrometer). Since there are fluctuations in concentration, the measured values may differ depending on how the measurement points are taken. The specific resistance is determined by measuring the resistance between two points on the surface. The specific resistance is determined for the current across the structure of ZHZYZH. Since the specific resistances of Z, H, and Y are different, the measured specific resistance is a weighted average of the specific resistances of Z, H, and Y. The specific resistance of Y alone and the specific resistance of Z alone are not known.

Since H and Z have the same specific resistance and H << Z, the ratio of the width of (H + Z) between two points of resistance measurement and the width of Y is expressed by z: y. Normalize as y + z = 1. When the oxygen and silicon concentrations in Z are [O] _z and [Si] _z and the oxygen and silicon concentrations in Y are [O] _y and [Si] _y , the measured specific resistance r is
r = (1 / μe) {z / (Mo [O] _z + Ms [Si] _z ) + y / (Mo [O] _y + Ms [Si] _y )}
It can be written as follows. According to the experiments by the present inventors, it was found that Si enters the C surface and the F surface in the same way. Those passing through the C plane enter Y, and those passing through the F plane enter Z. So it is [Si] _z = [Si] _y . It has been found by experiments of the present inventor that oxygen enters the F plane but does not enter the C plane. That is not the difference of about 50 times as described in Patent Document 7. That is [O] _y = 0. When the two characteristics are known, the above specific resistance equation is further simplified. Writing [Si] _z = [Si] _y = [Si] and writing [O] _z = [O]
r = (1 / μe) {z / (Mo [O] + Ms [Si]) + y / (Ms [Si])}
When written in this way, the relationship between the oxygen and silicon concentrations of the present invention and the specific resistance becomes more intuitive.

  A material having a small specific resistance r and a material having a high electrical conductivity σ is desired as the (rσ = 1) n-type substrate. When [O] and [Si] are determined, the specific resistance is lowest when z: y = 1: 0 from the above formula. In other words, it is better to cover the entire surface with the F surface. It is to grow while maintaining facets until the end. This means that the C-plane growth region Y is not made as much as possible.

  Type II fits that. As shown in FIG. 20, the valley-and-valley structure is maintained until the end, and the low-defect single crystal region Z is superior. As will be shown later, the specific resistance of the type II (Yamatani) tends to be lower than the type I (flat).

  Even if it is called type II, in the case of a dot mask, the C-plane growth region Y cannot be made zero due to geometric constraints. The C-plane growth region Y always occurs in the middle part of the mask. It acts to increase the specific resistance. In the case of the II type stripe mask, Y can be set to 0 because it is a parallel coating. Therefore, in the case of a type II stripe mask, a crystal with the lowest specific resistance should be made.

It can be seen that type II is suitable for producing a low resistivity, high conductivity n-type crystal. This is because the minimum specific resistance is given when [O] and [Si] are determined. Type II can be produced at 5/3 group ratio b of 1 to 10 and temperatures of 1040 ° C to 1080 ° C.
However, since the dot mask has no strength anisotropy, it has the advantage of a low crack generation rate.

  On the other hand, Type II, which maintains the facet structure until the end, has drawbacks. The facets may be {11-22}, {1-101}, {11-21}, {1-102}, etc., but generally have a steep angle の of about 50 ° to 60 ° with respect to the C plane. Eggplant. Since the mountain is made with the width w of the exposed portion E, the height of the mountain is (w / 2) tan Υ. For example, if Υ = 55 °, tan Υ = 1.43, so the height of the mountain is 0.71w. When w is large and 1500 μm = 1.5 mm, the height of the mountain is 1 mm. The crest portion is ground and flattened, and then polished to form a substrate. So the mountains are wasted. Type II, which maintains a high facet until the end, has the disadvantage that many parts are wasted.

  From this point of view, the type I that eventually grows with a flat C-plane has the advantage that it has less waste and is more economical. Type I can be produced at a 5/3 group ratio b of 1 to 10 and a temperature of 1080 to 1150 ° C. Even if it says a flat C surface, unlike C surface growth (it is not facet growth, 1030 degreeC or less) of patent documents 2, 3, it can be modeled on a board | substrate with few curvature and a low crack generation rate. Since the ideal I type is z: y = 0: 1, the specific resistance of the I type increases when [O] and [Si] are determined. Even if the specific resistance is large, it is the surface and the specific resistance is small in the depth direction. When used as a device substrate, current flows in the vertical direction. Therefore, it is important that the specific resistance in the vertical direction is low. Type I is initially facet grown and is initially doped with a large amount of oxygen, so the conductivity in the depth direction (vertical direction) is sufficiently high.

  The mixed mold made at 1070 ° C. to 1090 ° C. (FIG. 24) has both advantages and disadvantages. The specific resistance is medium, and the height that is wasted by grinding is also medium. Warpage and crack generation rates are also intermediate.

A dot mask or a stripe mask was formed using GaAs on the (111) Ga surface as a base substrate. The mask is SiO ₂ and the thickness is 60 nm to 200 nm. The dimensions (s, w, p) of the mask are 10 μm ≦ s ≦ 100 μm and 250 μm ≦ w ≦ 10000 μm. The mask dimension shape of each sample will be described later. A GaN film was grown thereon by the HVPE method. First, a buffer layer was formed, and then a thick epitaxial growth layer was formed. The number of different samples is 45. The conditions of the first buffer layer are as follows.

Conditions for buffer layer growth
Substrate temperature 500 ° C to 550 ° C
GaCl partial pressure P _GaCl = 80 Pa (0.0008 atm)
NH ₃ partial pressure P _NH3 = 16 kPa (0.16 atm)
Buffer layer thickness 50nm

The 5/3 group ratio b during the growth of the buffer layer is b = 200. In the present invention, importance is attached to the growth temperature and the 5/3 group ratio b, which is a value at the time of epitaxial growth (thick film growth), and the 5/3 group ratio b at the time of forming the buffer layer is not a problem.

In the substrate, “crack occurred” means that when a surface linear crack with a length of 2.0 mm or more occurs or when three or more surface linear cracks with a length of 0.5 mm to 2.0 mm occur. Or, it means that 21 or more surface linear cracks of 0.3 mm to 0.5 mm occurred.

In the substrate, “crack does not occur” means that surface linear cracks of 2.0 mm or more are 0, linear cracks of 0.5 mm to 2.0 mm are 2 or less, and 0.3 mm to 0 It means that there are 20 or less 5 mm cracks.

The crack generation rate (%) is a value obtained by dividing the number of grown substrates by the number of the total number of substrates and multiplying by 100. The donor density D refers to the concentration of n-type impurities. In other words, the donor density D is the concentration of silicon and oxygen that form the donor level. Both the oxygen concentration [O] and the silicon concentration [Si] were measured by SIMS (Secondary Ion Mass Spectrometer).

The warpage U of the substrate is expressed by a radius of curvature (m). The curvature is its reciprocal U ⁻¹ (m ⁻¹ ). The smaller the radius of curvature, the greater the warp. The warp may be expressed by a bulge h at the center of the wafer of diameter D, but there is a relationship of h = D ² / 8U in the range of quadratic curve approximation. For a 2-inch wafer (D = 50 mm), h (μm) = 312 / U (m).

Many experiments were repeated by changing the mask size, shape, growth temperature, NH ₃ partial pressure, GaCl partial pressure, SiH ₄ partial pressure, and the amount of water added. The substrate dimensions are 18 mm square for sample 1 only, sample 3 is 3 inches (75 mm) in diameter, and the other is a 2 inch (50 mm) diameter circular substrate.

Here, 45 samples are described. A serial number from 1 to 45 is assigned to each sample. 1-39 are examples of the present invention. Samples 40 to 45 are comparative examples. Of the examples of samples 1 to 39, samples 1 to 24 are type I (flat surface). In the case of type I, the surface is flat and the C surface is exposed. So to measure the oxygen concentration _{O C} and Si concentration Si _C in C plane. Samples 25-39 are type II (Yamagata). In the case of type II, the surface is uneven and has an inclined surface and a flat surface. The inclined surface is a facet surface F (sometimes referred to as an F surface). The flat surface is the C surface. Since the oxygen (O) concentration on both surfaces and the Si concentration were different, the oxygen concentration and Si concentration on both surfaces (C, F) were measured. The oxygen concentration in the C-plane and _{O C,} the Si concentration and Si _C. The oxygen concentration on the F plane is O _F and the Si concentration is Si _F.

In comparison with the above-mentioned symbols, O _C = [O] _y , Si _C = [Si] _y , O _F = [O] _z , and Si _F = [Si] _z . Samples 1 to 18 and 25 to 36 are provided with a stripe (parallel stripe) mask. In this case, s means the width of the mask covering portion, and w means the distance in the horizontal direction of the mask. s + w is the pitch P. Samples 19 to 24 and 37 to 39 have dot masks (isolated dots) attached to the base substrate. In this case, s means the diameter of the dotted mask, and w means the nearest mask interval. Since there are point masks at the center and apex positions of the regular hexagon, which is repeated, the dot mask can be completely defined only by s and w.

  In Comparative Examples 40 to 43, the mask is not attached to the base substrate, but the crystal is vapor-phase grown (C-plane growth as a whole) directly on the flat base substrate. Comparative Examples 40 to 43 were not specifically used in the prior art because they were specifically experimented to confirm the influence of the mask. Comparative Examples 44 to 45 were grown under the same conditions as the present invention without supplying Si source gas, and the specific resistance of the C plane was too high to be used as an n-type substrate. Comparative examples 44 and 45 show that oxygen alone is not sufficient, and a source gas containing Si is necessary.

In Table 1, the core means a coating or a crystal grown on the coating. Table 1 shows the sample number, pattern, core interval w (μm), core width s (μm), growth temperature Tq (° C.), P _Ga (GaCl partial pressure P _GaCl ; kPa), P _N (ammonia partial pressure P _NH3 KPa), substrate dimensions (mm) or inches (″), thickness (μm), core type (crystal type of the portion formed on the mask: inversion layer J, polycrystalline layer P or inclined layer A), crystal Surface type (type I or type II), Si density Si _C (cm ⁻³ ) at the C plane, oxygen density O _C (cm ⁻³ ) at the C plane, Si density Si _F (cm ⁻ at the facet plane F) ³ ) Oxygen density O _F (cm ⁻³ ), specific resistance (Ωcm), crack occurrence rate K (%), and curvature radius U (m) of warpage are shown. Although it is sometimes expressed as warp U, it is a radius of curvature and has a large value. As the warp is slight.
Oxygen as an n-type impurity is provided by adding water to any of the source gases. Silicon is provided by SiH ₄ gas. The amount of water added and the partial pressure of the SiH ₄ gas are varied. These are very small and difficult to measure. For that reason, it was not measured and not listed in Table 1. Even if the substrate temperature Tq and the s, w, p, NH ₃ , and GaCl partial pressures of the coating are the same, the amount of water added and the SiH ₄ partial pressure are different, so the Si, O doping amount, specific resistance r, warpage U, cracks The incidence K varies from sample to sample.

[Sample 1 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask (core) width of s = 50 μm was formed on an 18 mm square GaAs substrate. A feature of Sample 1 is that a rectangular wafer of 18 mm square is used as the base substrate. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The 5/3 group ratio b is b = 2.5. The crystal type of the core is the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 1%. The crack occurrence rate K is extremely low. The smallest of all samples. Warpage is U = 8 m. The warpage is extremely small. It is an excellent conductive GaN substrate.

[Sample 2 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). A 2 inch diameter circular GaAs substrate is readily available. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The 5/3 group ratio b is b = 2.5. The crystal type of the core is the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 7%. Crack generation rate K is low. Warpage is U = 6.2 m. Warpage is small. It is an excellent conductive GaN substrate.

[Sample 3 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 3 inches (75 mm). A feature of Sample 3 is that a wide 3-inch GaN wafer is used as a base substrate. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The 5/3 group ratio b is b = 2.5. The crystal type of the core is the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 12%. Crack generation rate K is low. Warpage is U = 5.2 m. Warpage is small. It is an excellent conductive GaN substrate having a large area.

[Sample 4 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 10 kPa (0.1 atm) until the thickness reached 400 μm or more. A characteristic of the sample 4 is that the GaCl partial pressure is high.

The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The 5/3 group ratio b is b = 1. The crystal type of the core is the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁹ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 10 ⁴ . Since the C plane has grown, the oxygen uptake is small. The specific resistance was 4.7 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 15%. Crack generation rate K is low. Warpage is U = 5 m. Warpage is small. It is an excellent conductive GaN substrate having a large area.

[Sample 5 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 3.3 kPa (0.033 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 3. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core is the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 13%. Crack generation rate K is low. Warpage is U = 6.2 m. Warpage is small. It is an excellent conductive GaN substrate.

[Sample 6 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core is the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁷ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^2. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 1 × 10 ⁻² Ωcm. Although the specific resistance was the highest among the samples, it was still a sufficiently low conductive substrate. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 3%. The crack occurrence rate K is extremely low. Warpage is U = 6.5 m. Warpage is small. It is an excellent conductive GaN substrate.

[Sample 7 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core is the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 5 × 10 ¹⁹ cm ⁻³ and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 5 × 10 ⁴ . Since the C plane has grown, the oxygen uptake is small. The specific resistance was 1.8 × 10 ⁻³ Ωcm. The specific resistance was extremely low and the substrate was conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 17%. The crack occurrence rate K is sufficiently low. Warpage is U = 4.7 m. The warpage is small enough. It is an excellent conductive GaN substrate.

[Sample 8 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the polycrystalline layer P. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 9%. Crack generation rate K is low. Warpage is U = 6.2 m. Warpage is small. It is an excellent conductive GaN substrate.

[Sample 9 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was graded layer A. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 11%. Crack generation rate K is low. Warpage is U = 6.2 m. Warpage is small. It is an excellent conductive GaN substrate.

[Sample 10 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 10 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). A characteristic of the sample 10 is that the mask width s is extremely small. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 11%. Crack generation rate K is low. Warpage is U = 6.2 m. Warpage is small. It is an excellent conductive GaN substrate. This means that even if the mask width is as narrow as 10 μm, a desired structure can be formed and an n-type conductive substrate can be produced.

[Sample 11 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 25 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). A characteristic of the sample 11 is that the mask width s is small. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 9%. Crack generation rate K is low. Warpage is U = 6.2 m. Warpage is small. It is an excellent conductive GaN substrate. Even if the mask width is as narrow as 25 μm, a desired structure can be formed and an n-type conductive substrate can be made.

[Sample 12 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 500 μm and a mask width of s = 100 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). A characteristic of the sample 12 is that the mask width s is wide. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 8%. Crack generation rate K is low. Warpage is U = 6.4 m. Warpage is small. It is an excellent conductive GaN substrate. Even if the mask width is as wide as 100 μm, a desired structure can be formed and an n-type conductive substrate can be made.

[Sample 13 (Example; stripe; type I)]
A parallel stripe mask having a stripe mask interval w of w = 250 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). A feature of the sample 13 is that the stripe core (mask) interval w is small. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 6%. The crack occurrence rate K is very low. Warpage is U = 6.8 m. Warpage is small. It is an excellent conductive GaN substrate. Even if the stripe mask interval w is as small as 250 μm, a desired structure can be formed and an n-type conductive substrate can be manufactured.

[Sample 14 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 750 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). A characteristic of the sample 14 is that the stripe core interval w is wide. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 8%. Crack generation rate K is low. Warpage is U = 6.2 m. Warpage is small. It is an excellent conductive GaN substrate. Even if the stripe mask interval w is as wide as 750 μm, a desired structure can be formed and an n-type conductive substrate can be manufactured.

[Sample 15 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 1000 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). A characteristic of the sample 15 is that the stripe core interval w is wide. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 11%. Crack generation rate K is low. Warpage is U = 5.3 m. Warpage is small. It is an excellent conductive GaN substrate. Even if the stripe mask interval w is as wide as 1000 μm (1 mm), a desired structure can be formed and an n-type conductive substrate can be produced.

[Sample 16 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 1500 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). A feature of the sample 16 is that the stripe core interval w is wide. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 13%. Crack generation rate K is low. Warpage is U = 4.7 m. The warpage is small enough. It is an excellent conductive GaN substrate. Even if the stripe mask interval w is as wide as 1500 μm (1.5 mm), a desired structure can be formed and an n-type conductive substrate can be produced.

[Sample 17 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 2000 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). A characteristic of the sample 17 is that the stripe core interval w is wide. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 17%. The crack occurrence rate K is sufficiently low. Warpage is U = 4.2 m. The warpage is small enough. It is an excellent conductive GaN substrate. Even if the stripe mask interval w is as wide as 2000 μm (2.0 mm), a desired structure can be formed and an n-type conductive substrate can be produced.

[Sample 18 (Example; stripe; type I)]
A parallel stripe mask having a stripe core interval w of w = 10000 μm and a mask width of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). A characteristic of the sample 18 is that the stripe core interval w is wide. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 22%. The crack occurrence rate K is sufficiently low. Warpage is U = 4 m. The warpage is small enough. It is an excellent conductive GaN substrate. Even when the stripe mask interval w is as wide as 10000 μm (10 mm), a desired structure can be formed and an n-type conductive substrate can be produced.

  When comparing Samples 16, 17, and 18, a conductive GaN substrate having a desired structure can be made up to a mask interval of about 10000 μm. However, as the mask interval w increases, the generation of cracks increases and the warpage increases gradually. I understand that. It can be seen that a good crystal structure is provided in a wide range where the mask interval w of the stripe mask is 250 μm to 10,000 μm.

  Samples 1 to 18 described above are obtained by providing a stripe mask and forming an I-type (flat surface) structure crystal thereon. Thereafter, examples of dot masks in Samples 19 to 24 will be described.

[Sample 19 (Example; dot; type I)]
A dot mask having a dot core interval w of w = 500 μm and a mask diameter of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). The dot mask is an isolated point mask (cover) at a 6-fold symmetrical position, and is arranged by laying out equilateral triangles and distributing the mask at the vertices. The mask is defined only by s and w. can do. It shows that the present invention can be applied to both a stripe mask and a dot mask. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 4%. The crack occurrence rate K is extremely low. Warpage is U = 4.8 m. The warpage is small enough. It is an excellent conductive GaN substrate. Even with a dot mask, a similar structure can be produced to produce a GaN substrate with excellent conductivity.

[Sample 20 (Example; Dot; Type I)]
A dot mask having a dot core interval w of w = 500 μm and a mask diameter of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). It shows that the present invention can be applied to both a stripe mask and a dot mask. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 4 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 4 × 10 ³ . Since the C plane has grown, the oxygen uptake is small. The specific resistance was 7 × 10 ⁻³ Ωcm. The specific resistance was a low and conductive substrate. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 5%. The crack occurrence rate K is extremely low. Warpage is U = 4.2 m. The warpage is small enough. It is an excellent conductive GaN substrate. Even with a dot mask, a similar structure can be produced to produce a GaN substrate with excellent conductivity.

[Sample 21 (Example; dot; type I)]
A dot mask having a dot core interval w of w = 500 μm and a mask diameter of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). It shows that the present invention can be applied to both a stripe mask and a dot mask. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 7 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 7 × 10 ³ . Since the C plane has grown, the oxygen uptake is small. The specific resistance was 5 × 10 ⁻³ Ωcm. The specific resistance was a low and conductive substrate. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 7%. Crack generation rate K is low. Warpage is U = 3.8 m. The warpage is small enough. It is an excellent conductive GaN substrate. Even with a dot mask, a similar structure can be produced to produce a GaN substrate with excellent conductivity.

[Sample 22 (Example; dot; type I)]
A dot mask having a dot core interval w of w = 1000 μm and a mask diameter of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). The sample 22 is characterized by a wide dot interval w. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 9%. Crack generation rate K is low. Warpage is U = 3.7 m. The warpage is small enough. It is an excellent conductive GaN substrate. Even if the dot interval is wide with a dot mask (w = 1000 μm), a similar structure can be formed and a GaN substrate excellent in conductivity can be made.

[Sample 23 (Example; dot; type I)]
A dot mask having a dot core interval w of w = 2500 μm and a mask diameter of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). The sample 23 is characterized by a wide dot interval w. After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. Crack generation rate K was 10%. Crack generation rate K is low. Warpage is U = 3.7 m. The warpage is small enough. It is an excellent conductive GaN substrate. Even if the dot interval is wide with a dot mask (w = 2500 μm), a similar structure can be formed and a GaN substrate excellent in conductivity can be made.

[Sample 24 (Example; dot; type I)]
A dot mask having a dot core interval w of w = 5000 μm and a mask diameter of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). The sample 24 is characterized by a very wide dot interval w (5 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1100 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type I. Since the growth temperature Tq was high, it became I type. Since it is I type, the surface is flat and only the C surface is exposed. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. Since the C plane has grown, the oxygen uptake is small. The specific resistance was 9 × 10 ⁻³ Ωcm. The specific resistance was low and the substrate was sufficiently conductive. The donor generating n-type carriers (conducting electrons) is mainly Si. The crack occurrence rate K was 13%. Crack generation rate K is low. The warpage is U = 3.5 m. The warpage is small enough. It is an excellent conductive GaN substrate. Even if the dot interval is wide with a dot mask (w = 5000 μm), a GaN substrate having a similar structure and excellent conductivity can be produced.

  Looking at the samples 19 to 24 using the dot mask, it is possible to create a good GaN substrate having a predetermined structure with a dot mask interval w of 500 μm to 5000 μm and less warpage and less warpage. Looking at Samples 22 to 24, the crack generation rate tends to increase as w increases. When a device is to be formed thereon, a wider w is better because a wider w has less locational restrictions. Even when w = 10000 μm, the occurrence of cracks is acceptable. Even if w is 250 μm at the narrowest limit of w, an excellent GaN substrate can be provided. Speaking only from the nature of the substrate, a GaN substrate crystal with conductivity and a small amount of cracking and small warpage can be produced in a wide range of dot mask intervals of about 250 μm to 10000 μm.

Samples 1 to 24 described above were crystal substrates grown at a higher temperature with a growth temperature of Tq = 1100 ° C., but samples 25 to 45 described below have a growth temperature of Tq = 1050 ° C. or higher. It is a crystal grown at the following low temperature. The crystal grown at 1050 ° C. has a structure in which the surface includes irregularities of mountains and valleys (stripe mask) or concave portions of conical pits. It is a surface rich in irregularities with many inclined facet surfaces F exposed. This is type II. The flat surface is the C surface and the inclined surface is the facet surface F. There is anisotropy in oxygen doping. In the case of type II, a large amount of oxygen is doped from the facet plane F. So the oxygen concentration O _F in facet F, the oxygen concentration O _C in C plane different. Therefore to measure both oxygen concentration O _F in an oxygen concentration O _C and facets F in C plane. The oxygen concentration at the facet plane is greater than the oxygen concentration at the C plane (O _F > O _C ). The Si concentration is also measured on both the facet plane F and the flat plane C plane. The Si concentration does not seem to be selective on the C and F planes.

[Sample 25 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface includes a faceted surface F and a flat C surface, and has a sawtooth-like surface where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. The Si density on the F plane is Si _F = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _F = 1 × 10 ¹⁸ / cm ³ . The Si / O ratio (g) on the F plane is g = 1. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. Oxygen has a significant difference between the C-plane and F-plane, and is highly anisotropic. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference in the C and F planes, and Si is indiscriminate. In the sample 25, the oxygen concentration on the F plane is almost equal to the Si concentration. The specific resistance was equal to 8 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a low and uniform conductive substrate. The donor generating n-type carriers (conducting electrons) is mainly Si on the C plane, but oxygen and Si are considered to contribute equally to the F plane. The crack occurrence rate K was 6%. The crack occurrence rate K is very low. Warpage is U = 6.5 m. Warpage is small. It is an excellent conductive GaN substrate. Even with a type II crystal having a superposition type mountain range structure, oxygen is doped in the F plane and Si is doped in the C plane, so that a complementary carrier is provided. I can get it.

[Sample 26 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface includes a faceted surface F and a flat C surface, and has a sawtooth-like surface where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 4 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 4 × 10 ³ . The Si density on the F plane is Si _F = 4 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _F = 1 × 10 ¹⁸ / cm ³ . The Si / O ratio (g) on the F plane is g = 4. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. Oxygen has a significant difference between the C-plane and F-plane, and is highly anisotropic. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si is indiscriminate on the C and F planes. The specific resistance was 6 × 10 ⁻³ Ωcm equally in both the F-plane portion and the C-plane portion. The specific resistance was a low and uniform conductive substrate. The main donor generating n-type carriers (conduction electrons) is Si on both the C and F planes. The crack occurrence rate K was 8%. Crack generation rate K is low. Warpage is U = 6.3 m. Warpage is small. Even in a type II crystal having a plurality of mountain ranges, Si is doped to substantially the same degree on both the F and C planes to give an n-type carrier, so that the specific resistance does not change between the F and C planes. A uniform conductive substrate crystal can be obtained.

[Sample 27 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface includes a faceted surface F and a flat C surface, and has a sawtooth-like surface where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 7 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 7 × 10 ³ . The Si density on the F plane is Si _F = 7 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _F = 1 × 10 ¹⁸ / cm ³ . The Si / O ratio (g) on the F plane is g = 7. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 4 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a low and uniform conductive substrate. The main donor generating n-type carriers (conduction electrons) is Si on both the C and F planes. The crack occurrence rate K was 11%. Crack generation rate K is low. Warpage is U = 6.2 m. Warpage is small. Even in a type II crystal having a plurality of parallel mountain ranges, Si is doped to substantially the same degree on both the F and C planes to give an n-type carrier, so that the specific resistance does not change between the F and C planes. A uniform conductive substrate crystal can be obtained.

[Sample 28 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 1 × 10 ¹⁹ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 10 ⁴ . The Si density on the F plane is Si _F = 1 × 10 ¹⁹ cm ⁻³ , and the oxygen concentration is O _F = 1 × 10 ¹⁸ / cm ³ . The Si / O ratio (g) on the F plane is g = 10. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 2 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a very low and uniform conductive substrate. The main donor generating n-type carriers (conduction electrons) is Si on both the C and F planes. The crack occurrence rate K was 12%. Crack generation rate K is low. Warpage is U = 6 m. Warpage is small. Even in a type II crystal having a plurality of parallel mountain ranges, Si is doped to substantially the same degree on both the F and C planes to give an n-type carrier, so that the specific resistance does not change between the F and C planes. A uniform conductive substrate crystal can be obtained.

[Sample 29 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. The Si density on the F plane is Si _F = 1 × 10 ^18.
m ⁻³ , the oxygen concentration is O _F = 5 × 10 ¹⁶
/ Cm ³ . The Si / O ratio (g) on the F plane is g = 20. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 8 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a low and uniform conductive substrate. The main donor generating n-type carriers (conduction electrons) is Si on both the C and F planes. The crack occurrence rate K was 5%. The crack occurrence rate K is extremely low. Warpage is U = 6.4 m. Warpage is small. Even in a type II crystal having a plurality of parallel mountain ranges, Si is doped to substantially the same degree on both the F and C planes to give an n-type carrier, so that the specific resistance does not change between the F and C planes. A uniform conductive substrate crystal can be obtained.

[Sample 30 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. The Si density on the F plane is Si _F = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _F = 1 × 10 ¹⁷ / cm ³ . The Si / O ratio (g) on the F plane is g = 10. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 7.9 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a low and uniform conductive substrate. The main donor generating n-type carriers (conduction electrons) is Si on both the C and F planes. The crack occurrence rate K was 5%. The crack occurrence rate K is extremely low. Warpage is U = 6.3 m. Warpage is small. Even in a type II crystal having a plurality of parallel mountain ranges, Si is doped to substantially the same degree on both the F and C planes to give an n-type carrier, so that the specific resistance does not change between the F and C planes. A uniform conductive substrate crystal can be obtained.

[Sample 31 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. The Si density on the F plane is Si _F = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _F = 5 × 10 ¹⁷ / cm ³ . The Si / O ratio (g) on the F plane is g = 2. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 7.5 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a low and uniform conductive substrate. The main donor generating n-type carriers (conduction electrons) is Si on both the C and F planes. The crack occurrence rate K was 6%. The crack occurrence rate K is very low. Warpage is U = 6.2 m. Warpage is small. Even in a type II crystal having a plurality of parallel mountain ranges, Si is doped to substantially the same degree on both the F and C planes to give an n-type carrier, so that the specific resistance does not change between the F and C planes. A uniform conductive substrate crystal can be obtained.

[Sample 32 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. The Si density on the F plane is Si _F = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _F = 5 × 10 ¹⁸ / cm ³ . The Si / O ratio (g) on the F plane is g = 0.2. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 7.5 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a low and uniform conductive substrate. The main donors generating n-type carriers (conducting electrons) are Si on the C plane and O on the F plane. The crack occurrence rate K was 7%. Crack generation rate K is low. Warpage is U = 6 m. Warpage is small. Even in a type II crystal having a plurality of parallel mountain ranges, Si is doped to substantially the same degree on both the F and C planes to give an n-type carrier, so that the specific resistance does not change between the F and C planes. A uniform conductive substrate crystal can be obtained.

[Sample 33 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. The Si density on the F plane is Si _F = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _F = 1 × 10 ¹⁹ / cm ³ . The Si / O ratio (g) on the F plane is g = 0.1. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen (O) has preference in the C and F planes, and Si has non-preference in the C and F planes. The specific resistance was approximately equal to 2 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a very low and uniform conductive substrate. The main donors generating n-type carriers (conducting electrons) are Si on the C plane and O on the F plane. Crack generation rate K was 10%. Crack generation rate K is low. Warpage is U = 5.8 m. Warpage is small. It is a type II crystal having a plurality of parallel mountain ranges, and Si is doped to approximately the same degree on both the F plane and the C plane, and oxygen doping is predominant on the F plane. Both the F surface and the C surface become conductive.

[Sample 34 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 4 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 4 × 10 ³ . The Si density on the F plane is Si _F = 4 × 10 ¹⁸ cm ⁻³ and the oxygen concentration is O _F = 1 × 10 ¹⁹ / cm ³ . The Si / O ratio (g) on the F plane is g = 0.4. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 1.9 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was very low and the substrate was uniformly conductive. The main donors generating n-type carriers (conducting electrons) are Si on the C plane and O on the F plane. The crack occurrence rate K was 11%. Crack generation rate K is low. Warpage is U = 5.5 m. Warpage is small. A type II crystal having a plurality of parallel mountain ranges, Si is doped to approximately the same degree on both the F and C planes, the F plane is doped with oxygen at a high concentration, and both the C and F planes are highly conductive substrate crystals. Obtainable.

[Sample 35 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 7 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 7 × 10 ³ . The Si density on the F-plane is Si _F = 7 × 10 ¹⁸ cm ⁻³ and the oxygen concentration is O _F = 1 × 10 ¹⁹ / cm ³ . The Si / O ratio (g) on the F plane is g = 0.7. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equally 1.8 × 10 ⁻³ Ωcm in both the F-plane portion and the C-plane portion. The specific resistance was very low and the substrate was uniformly conductive. The main donors generating n-type carriers (conducting electrons) are Si on the C plane and O on the F plane. The crack occurrence rate K was 14%. The crack occurrence rate K is sufficiently low. Warpage is U = 5 m. Warpage is small. A type II crystal having a plurality of parallel mountain ranges, Si is doped to approximately the same degree on both the F and C planes, the F plane is doped with oxygen at a high concentration, and both the C and F planes are highly conductive substrate crystals. Obtainable.

[Sample 36 (Example; stripe; type II)]
A stripe mask having a stripe mask core interval w of w = 500 μm and a mask width s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 1 × 10 ¹⁹ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 10 ⁴ . The Si density on the F plane is Si _F = 1 × 10 ¹⁹ cm ⁻³ , and the oxygen concentration is O _F = 1 × 10 ¹⁹ / cm ³ . The Si / O ratio (g) on the F plane is g = 1. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 1.5 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. Both oxygen and Si were doped at a high concentration, and the resistivity was very low and the substrate had a uniform conductivity. The main donors generating n-type carriers (conducting electrons) are Si on the C plane and O and Si on the F plane. The crack occurrence rate K was 18%. The crack occurrence rate K is sufficiently low. Warpage is U = 4.8 m. Warpage is slightly small. A type II crystal having a parallel mountain range structure, in which Si is doped to approximately the same degree on both the F plane and the C plane, the F plane is doped with oxygen at a high concentration, and a substrate crystal having high conductivity on both the C plane and the F plane is obtained. be able to.
Samples 25 to 36 described above are obtained by forming a type II crystal by providing a stripe mask. In the present invention, a similar type II crystal can be formed by providing a dot mask on the base substrate. Samples 37 to 39 are obtained by the dot mask method.

[Sample 37 (Example; dot; type II)]
A dot mask having a dot mask core interval w of w = 500 μm and a dot diameter s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. The Si density on the F plane is Si _F = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _F = 1 × 10 ¹⁸ / cm ³ . The Si / O ratio (g) on the F plane is g = 1. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 8 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a low and uniform conductive substrate. The main donors generating n-type carriers (conducting electrons) are Si on the C plane and O and Si on the F plane. The crack occurrence rate K was 3%. The crack occurrence rate K is very low. Warpage is U = 5 m. Warpage is slightly small. A type II crystal having a structure having a large number of isolated defect gathering regions H at equal intervals, Si is doped to approximately the same degree on both the F plane and the C plane, the F plane is more heavily doped with oxygen, and the C plane is also an F plane. In addition, a substrate crystal having high conductivity can be obtained.

[Sample 38 (Example; Dot; Type II)]
A dot mask having a dot mask core interval w of w = 500 μm and a dot diameter s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 4 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 4 × 10 ³ . The Si density on the F plane is Si _F = 4 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _F = 1 × 10 ¹⁸ / cm ³ . The Si / O ratio (g) on the F plane is g = 4. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 6.3 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a low and uniform conductive substrate. The main donors generating n-type carriers (conduction electrons) are Si on the C plane and Si on the F plane. The crack occurrence rate K was 5%. The crack occurrence rate K is very low. Warpage is U = 4.6 m. Warpage is slightly small. A type II crystal having a structure having a large number of isolated defect gathering regions H at equal intervals, Si is doped to approximately the same degree on both the F plane and the C plane, the F plane is more heavily doped with oxygen, and the C plane is also an F plane. In addition, a substrate crystal having high conductivity can be obtained.

[Sample 39 (Example; Dot; Type II)]
A dot mask having a dot mask core interval w of w = 500 μm and a dot diameter s of s = 50 μm was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, epitaxial growth was performed. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal type of the core was the inversion layer J. The crystal face type is type II. Since the growth temperature Tq (1050 ° C.) was low, it became type II. Since it is type II, the surface has a facet surface F and a flat C surface, and has a surface like a mountain range where mountains and valleys alternate. The surface is a mixture of C and F planes. The Si density on the C plane is Si _C = 7 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 7 × 10 ³ . The Si density on the F plane is Si _F = 7 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _F = 1 × 10 ¹⁸ / cm ³ . The Si / O ratio (g) on the F plane is g = 7. The C surface has a small oxygen uptake and the F surface has a large oxygen uptake. However, Si is doped to the same extent on the C and F planes, and there is no difference between the C and F planes. Oxygen has preference on the C and F planes, and Si has non-preference on the C and F planes. The specific resistance was equal to 4 × 10 ⁻³ Ωcm in both the F plane portion and the C plane portion. The specific resistance was a low and uniform conductive substrate. The main donors generating n-type carriers (conduction electrons) are Si on the C plane and Si on the F plane. The crack occurrence rate K was 6%. The crack occurrence rate K is very low. Warpage is U = 4.2 m. Warpage is slightly small. A type II crystal having a structure having a large number of isolated defect gathering regions H at equal intervals, Si is doped to approximately the same degree on both the F plane and the C plane, the F plane is more heavily doped with oxygen, and the C plane is also an F plane. In addition, a substrate crystal having high conductivity can be obtained.

[Sample 40 (comparative example; no mask; C-plane growth)]
A buffer layer was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm) without a mask and then epitaxially grown. Since no mask is attached, this is not an example but a comparative example. Although it is a comparative example, it is not a well-known example. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. There is no core because there is no mask. Flat C-plane growth was performed. It is neither type I nor type II. The surface is a uniform C-plane. There is no F-plane. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. The specific resistance was 0.01 Ωcm. The specific resistance is high and the conductivity is insufficient. The main donor generating n-type carriers (conduction electrons) is Si. The crack occurrence rate K was 75%. The crack occurrence rate K is very high. The warpage is U = 1.5 m. The warpage is very large. Since it has many cracks and large warpage, it cannot be used as a substrate for manufacturing devices.

[Sample 41 (comparative example; no mask; C-plane growth)]
A buffer layer was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm) without a mask and then epitaxially grown. Since no mask is attached, this is not an example but a comparative example. Although it is a comparative example, it is not a well-known example. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. There is no core because there is no mask. Flat C-plane growth was performed. It is neither type I nor type II. The surface is a uniform C-plane. There is no F-plane. The Si density on the C plane is Si _C = 1 × 10 ¹⁹ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 10 ⁴ . The specific resistance was 4.7 × 10 ⁻³ Ωcm. The specific resistance is low and the conductivity is sufficient. The main donor generating n-type carriers (conduction electrons) is Si. The crack occurrence rate K was 88%. The crack occurrence rate K is very high. The warpage is U = 1.2 m. The warpage is extremely large. Since it has many cracks and large warpage, it cannot be used as a substrate for manufacturing devices.

[Sample 42 (comparative example; no mask; C-plane growth)]
A buffer layer was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm) without a mask and then epitaxially grown. Since no mask is attached, this is not an example but a comparative example. Although it is a comparative example, it is not a well-known example. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1030 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. There is no core because there is no mask. Flat C-plane growth was performed. It is neither type I nor type II. The surface is a uniform C-plane. There is no F-plane. The Si density on the C plane is Si _C = 1 × 10 ¹⁸ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . Si / O ratio in the C-plane (q) is the q = 10 ^3. The specific resistance was 0.01 Ωcm. The specific resistance is high. The main donor generating n-type carriers (conduction electrons) is Si. The crack occurrence rate K was 92%. The crack occurrence rate K is very high. The warpage is U = 1.3 m. The warpage is extremely large. Since it has many cracks and large warpage, it cannot be used as a substrate for manufacturing devices.

[Sample 43 (comparative example; no mask; C-plane growth)]
A buffer layer was formed on a circular GaAs substrate having a diameter of 2 inches (50 mm) without a mask and then epitaxially grown. Since no mask is attached, this is not an example but a comparative example. Although it is a comparative example, it is not a well-known example. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1030 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. There is no core because there is no mask. Flat C-plane growth was performed. It is neither type I nor type II. The surface is a uniform C-plane. There is no F-plane. The Si density on the C plane is Si _C = 1 × 10 ¹⁹ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 10 ⁴ . The specific resistance was 4.7 × 10 ⁻³ Ωcm. Specific resistance is low. The main donor generating n-type carriers (conduction electrons) is Si. The crack occurrence rate K was 90%. The crack occurrence rate K is very high. Warpage is U = 1 m. The warpage is extremely large. Since it has many cracks and large warpage, it cannot be used as a substrate for manufacturing devices.

[Sample 44 (Comparative Example; Stripe; Type II)
A stripe mask having a stripe mask interval of w = 500 μm, a stripe width of s = 50 μm, and a pitch of 550 μm was attached on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, GaN was epitaxially grown with the SiH ₄ gas cut off. Since Si source gas is not supplied, it is not an example of the present invention. Although it is a comparative example, it is not a well-known example. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. It had the same periodic structure as the mask. The crystal on the core is the inversion layer J. The crystal type is type II. The Si density on the C plane is Si _C = 1 × 10 ¹⁶ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 10. The specific resistance on the C surface was high. The Si density on the F-plane is Si _C = 1 × 10 ¹⁶ cm ⁻³ , and the oxygen concentration is O _C = 4 × 10 ¹⁸ / cm ³ . The Si / O ratio (q) on the F plane is q = 1/400. The fact that the Si concentration was 10 ¹⁶ cm ⁻³ even though no Si raw material was given may indicate that Si remaining in the furnace entered the crystal. 10 ¹⁶ cm ⁻³ may be the detection limit of Si. Semi-insulating rather than conductive. The crack occurrence rate K was 30%. Crack generation rate K is low. Warpage is U = 7 m. Warpage is small. Since the resistivity is high, it cannot be used as a conductive substrate.

[Sample 45 (Comparative Example; Stripe; Type II]
A stripe mask having a stripe mask interval of w = 500 μm, a stripe width of s = 50 μm, and a pitch of 550 μm was attached on a circular GaAs substrate having a diameter of 2 inches (50 mm). After forming the buffer layer, GaN was epitaxially grown with the SiH ₄ gas cut off. Since no Si raw material is provided, it is not an example of the present invention. Although it is a comparative example, it is not a well-known example. Epitaxial growth was performed at an epitaxial growth temperature of Tq = 1050 ° C., NH ₃ partial pressure P _NH3 = 10 kPa (0.1 atm), and GaCl partial pressure P _GaCl = 4 kPa (0.04 atm) until the thickness reached 400 μm or more.

The 5/3 group ratio b is b = 2.5. The GaAs substrate was processed and removed to obtain a single independent substrate of GaN having a thickness of 400 μm. The crystal region had the same periodic structure as the mask. The crystal on the core is the inversion layer J. In the portion without the mask, the low-defect single crystal region Z and the C-plane growth region Y formed a ZYZ structure. The crystal type is type II. The Si density on the C plane is Si _C = 1 × 10 ¹⁶ cm ⁻³ , and the oxygen concentration is O _C = 1 × 10 ¹⁵ / cm ³ . The Si / O ratio (q) on the C plane is q = 10. The specific resistance on the C surface was high. The Si density on the F-plane is Si _C = 1 × 10 ¹⁶ cm ⁻³ , and the oxygen concentration is O _C = 8 × 10 ¹⁸ / cm ³ . The Si / O ratio (q) on the F plane is q = 1/800. The fact that the Si concentration was 10 ¹⁶ cm ⁻³ even though no Si raw material was given may indicate that Si remaining in the furnace entered the crystal. 10 ¹⁶ cm ⁻³ may be the detection limit of Si. Semi-insulating rather than conductive. The crack occurrence rate K was 36%. Crack generation rate K is low. Warpage is U = 6.8 m. Warpage is small. Since the resistivity on the C surface is high, it cannot be used as a conductive substrate.

  What are the values of the substrate temperature and the 5/3 group ratio b in the conventional examples so far? When citing and explaining patent documents, the growth temperature (substrate temperature) and the 5/3 group ratio b are listed and shown in FIG. 22 by black circles and black dots and white circles. The substrate temperature and the 5/3 group ratio b of the present invention are also shown in FIG. Thereby, the unique growth conditions of the present invention become clearer.

Regarding the type II of the present invention, the point of temperature 5/3 group ratio b is indicated by a white triangle. There are 15 points of 5/3 group ratio b = 2.5 at a temperature of 1050 ° C.

Regarding the type I of the present invention, the point of temperature 5/3 group ratio b is indicated by a white circle. There are 22 points of 5/3 group ratio b = 2.5 at a temperature of 1100 ° C. There is one 5/3 group ratio b = 3 at a temperature of 1100 ° C. There is one 5/3 group ratio b = 1 at a temperature of 1100 ° C.

The range of the substrate temperature of the present invention and the 5/3 group ratio b is surrounded by a broken line. 1080 ° C. is an intermediate mixing type temperature.

FIG. 23 shows the curvature radius (m) and the crack generation rate (%) of the samples 1 to 45 in two-dimensional coordinates. The horizontal axis represents the curvature radius (m) of the warp, and the vertical axis represents the crack generation rate (%). The numbers are sample numbers. Type I is indicated by white circles. Sample 1 is the best sample with a warp of 8 m and a crack generation rate of 1%. The warpage is 3.5 m for sample 24 and 3.7 m for samples 22 and 23. In type I, warpage U is distributed between 3.5 m and 8 m. The crack occurrence rate of the sample 18 is 22%, and the type I is in the range of 1% to 22%.
Type II is indicated by white triangles. The warp of the sample 39 is 4.2 m. Type II has a warpage of about 4.2 m to 6.5 m. The occurrence of cracks is less than Type I. 18% for sample 36 and 3% for sample 37. In the examples of Samples 1 to 39, the warpage is 3.5 m ≦ U ≦ 8 m. In the case of Type II, 4.2 m ≦ U ≦ 6.5 m. Type II crack occurrence rate K is 3% ≦ K ≦ 18%. Type II seems to be better in terms of both crack generation rate and warpage, but is not significantly different.
Comparative examples are indicated by x. Samples 40 to 43 have a high crack generation rate and large warpage. This indicates that a crystal having excellent mechanical properties with less internal stress, generation of cracks, and warpage can be obtained by providing a mask (covering portion) on the base substrate and performing facet growth. Samples 44 and 45 are comparative examples because they have little warpage and a low crack generation rate but a large specific resistance.

FIG. 27 shows the C-plane Si doping amount (cm ⁻³ ) of the sample and the surface specific resistance (Ωcm) as two-dimensional coordinates on a logarithmic graph paper. White circles indicate type I, white triangles indicate type II, and x indicates a comparative example. The numbers are sample numbers. There are I-type samples 1, 2, 3, 5, 8-19, and 22-24 at a C-plane Si concentration of 1 × 10 ¹⁸ cm ⁻³ and a specific resistance r = 0.0009 Ωcm. The number of samples is 19. Samples 25, 29, 30, 31, 32, and 37 are distributed around this type II. The total number of samples is 25. The specific resistance is measured on the surface, and since Si counts the number of Si atoms on the surface by SIMS, it is profitable that the specific resistance is the same if the Si concentration is the same for the I type. This is because the surface of the I-type that can absorb only Si on the C-plane has no oxygen action near the surface. Even in the type II having the F surface, samples 25, 29, 30, 31, and 37 have the same oxygen concentration at the F surface (facet) as the Si concentration (samples 25 and 37) or smaller than the Si concentration (sample) 29, 30, 31), the resistivity r is about 0.007 to 0.008 Ωcm when the C-plane (the same for the F-plane) Si concentration is 1 × 10 ¹⁸ cm ⁻³ . It is estimated that the slight difference from r = 0.09 Ωcm is due to oxygen doping on the F plane.
Sample 32 has an oxygen concentration of 5 × 10 ¹⁸ cm ⁻³ on the F surface and is greater than the Si concentration, but is 0.0075 Ωcm. This seems to be a measurement error.
Since the specific resistance should be inversely proportional to the carrier concentration, if the mobility is the same, the coordinate points of the Si concentration and specific resistance are Si = 1 × 10 ¹⁸ cm ⁻³ , r = 0.09Ωcm and Si = They should be arranged on a line connecting 10 ¹⁹ cm ⁻³ and r = 0.0009 Ωcm (FIG. 27; indicated by a broken line). Samples 20, 21, 4, and 7 are on the broken line even in type I. This means that even if the Si doping amount is increased, the specific resistance does not decrease proportionally (conductivity does not increase). This seems to be because as the doping amount increases, scattering increases and carrier mobility decreases. In the case of type II, the resistivity should decrease due to the contribution of oxygen, but the contribution of oxygen will be weak in type II samples 26, 38, 27, and 39 above the broken line because the oxygen concentration is lower than the Si concentration. .
The I-type sample 7 has a very high Si doping concentration of 5 × 10 ¹⁹ cm ⁻³ . Therefore, the specific resistance r = 0.018 Ωcm. It is a good substrate with high conductivity. This is the highest Si doping value throughout the sample. Even with such a high concentration of doping, Sample 7 has a warp of 4.7 m and a crack generation rate of 17%. Although cracking and warping are both large, they are still worth using. The reason why the structure does not collapse even when Si is doped at such a high concentration is that the internal structure of the heterogeneous structure HZYZH. When the surface is flat, if the C-plane is grown, the crack generation rate is not 100% as in Patent Documents 2 and 3, but the present invention makes the cover part and makes facet growth, so it finally has a flat surface. This means that the crystal is strong and the structure is solid even when doped with a high concentration of Si. The sample 7 far from the right end in FIG.
Type II sample 36 has a Si concentration of Si = 1 × 10 ¹⁹ cm ⁻³ , but the specific resistance is r = 0.015 Ωcm, which is the smallest among the samples. Excellent conductivity. This is because the oxygen concentration on the F-plane is O = 1 × 10 ¹⁹ cm ⁻³ and both the oxygen and Si concentrations are high. High oxygen concentration and Si concentration result in high conductivity σ = 667 / Ωcm. The conductivity σ is the reciprocal of the specific resistance. σ = r ⁻¹ . The sample 36 has a crack generation rate of 18% and a warpage of 4.8 m, and its mechanical properties are not so good, but it can still be used effectively.
The fact that oxygen is important for Type II can be seen by comparing Samples 28 and 36. In either case, Si = 1 × 10 ¹⁹ cm ⁻³ , but the oxygen concentration is different. Sample 28 has O = 1 × 10 ¹⁸ cm ⁻³ and sample 36 has O = 1 × 10 ¹⁹ cm ⁻³ . It can be considered that the difference between the specific resistance r = 0.002 Ωcm of the sample 28 and the specific resistance r = 0.015 Ωcm of the sample 36 is caused by the difference in oxygen amount.
The sample 33 has Si = 1 × 10 ¹⁸ cm ^−3, but has a specific resistance r = 0.002 Ωcm, which is about 1/5 smaller than the 25 samples of Samples 1, 2, 3,. This is because the specific resistance is lowered by the action of oxygen O. Since O = 1 × 10 ¹⁹ cm ⁻³ is 10 times as large as Si, the specific resistance will be lowered so much.
The maximum value of the specific resistance is r = 0.01 Ωcm, which is given by the sample 6. It is I type and Si = 1 × 10 ¹⁷ cm ⁻³ . Compared to the 25 samples (1, 2, 3,...) In the vicinity of Si = 1 × 10 ¹⁸ cm ⁻³ , the specific resistance should be about 0.09 Ωcm because the Si concentration is 1/10. The measured value is 0.01 Ωcm. Since sample 6 has a crack occurrence rate of 3% and a curvature radius of curvature of 6.5 m, Si = 1 × 10 ¹⁷ cm ⁻³ is assumed to be a correct measurement value with a small Si doping amount. Since SIMS measures the Si concentration at one fixed point, the Si concentration may fluctuate and the average concentration may be higher. Or there may be an error in the resistivity measurement. The range of the specific resistance r of the substrate of the present invention is 0.0015 Ωcm ≦ r ≦ 0.01 Ωcm.

FIG. 28 is a white triangle for type II samples 25-39 with the silicon concentration (cm ⁻³ ) on the F plane (facet) on the horizontal axis and the oxygen concentration (density) (cm ⁻³ ) on the F plane on the vertical axis. It is a graph.
Diagonal samples 25, 37, and 36 have the same F-plane silicon and oxygen concentration. Samples 25 and 37 are 1 × 10 ¹⁸ cm ⁻³ for both Si and O. The specific resistance is 8 × 10 ⁻³ Ωcm.
In the samples 31, 30, 29, 38, 26, 27, 39, and 28 below the diagonal line, the Si concentration is larger than the oxygen concentration (Si _F > O _F ). Samples 39 and 27 both have Si = 7 × 10 ¹⁸ cm ⁻³ and O = 1 × 10 ¹⁸ cm ⁻³ . The specific resistance is both 4 × 10 ⁻³ Ωcm. These results suggest that the resistivity is often equal when the Si and O concentrations on the F plane are equal. Samples 25, 37, 31, 30, and 29 in which Si = 1 × 10 ¹⁸ cm ⁻³ have an oxygen concentration of O ≦ 1 × 10 ¹⁸ cm ⁻³ , but have specific resistances of 8 ×, 8 ×, and 7.5. Since x, 7.9x, and 8x10 ^-3 Ωcm, the Si concentration largely dominates the specific resistance. This is because the oxygen concentration is low.
Samples 33, 34, 35, and 36 having an oxygen concentration of 10 × 10 ¹⁸ cm ⁻³ have specific resistances of 2 ×, 1.9 ×, 1.8 ×, and 1.5 × 10 ⁻³ Ωcm. Low resistance. Specific resistance is low (conductivity is high) due to high concentration oxygen. The difference in specific resistance may be due to the difference in Si concentration. The Si concentration is 1 × 4 ×, 7 ×, 10 × 10 ¹⁸ cm ⁻³ for the samples 33, 34, 35, and 36. It can be seen that the resistivity decreases when the oxygen concentration is high and the Si concentration is high.
Compare samples with the same Si concentration but different oxygen concentrations. Samples 36 and 28 both have a Si concentration of 10 × 10 ¹⁸ cm ⁻³ , but the oxygen concentration is 10 times different. Since the specific resistance is 1.5 × 2 × 10 ⁻³ Ωcm, it is 1.3 times different. Samples 35 and 27 both have a Si concentration of 7 × 10 ¹⁸ cm ⁻³ , but the oxygen concentration is 10 times different. Since the specific resistance is 1.8 × 4 × 10 ⁻³ Ωcm, it is 2.2 times different. Samples 33 and 25 both have a Si concentration of 1 × 10 ¹⁸ cm ⁻³ , but the oxygen concentration is 10 times different. Since the specific resistance is 2 ×, 8 × 10 ⁻³ Ωcm, it is four times different. From these results, in the case of type II, the resistivity decreases as the Si concentration and oxygen concentration on the F plane increase, but it may be inversely proportional to the square root rather than inversely proportional to the first order.

FIG. 29 is a graph showing the Si concentration on the C plane and the Si concentration on the F plane of Samples 25 to 39 of type II, with the horizontal axis and the vertical axis. Samples 25, 29, 30, 31, 32, 33, and 37 all have a Si concentration of 1 × 10 ¹⁸ cm ⁻³ and are equal on both the C plane and the F plane. Samples 26, 34, and 38 all have an Si concentration of 4 × 10 ¹⁸ cm ⁻³ and are equal on the C and F planes. Samples 27, 35, and 39 all have a Si concentration of 7 × 10 ¹⁸ cm ⁻³ and are equal on the C and F planes. Samples 36 and 28 both have a Si concentration of 10 × 10 ¹⁸ cm ⁻³ and are the same on the C and F planes. These coordinate points lie on a 45 ° diagonal. This means that Si enters the same amount on both the C and F planes. Si _F = Si _C This is equivalent to what was previously described [Si] _z = [Si] _y . This means that silicon has no surface orientation dependency. Silicon has no surface preference.

FIG. 30 shows the oxygen concentration on the F-plane and the oxygen concentration on the C-plane of Samples 25 to 39 of type II on the horizontal and vertical axes. The horizontal axis represents the oxygen concentration (cm ⁻³ ) on the F plane. The vertical axis represents the oxygen concentration (cm ⁻³ ) on the C plane. Samples 33, 34, 35, and 36 are 1 × 10 ¹⁹ cm ⁻³ on the F plane and 1 × 10 ¹⁵ cm ⁻³ on the C plane. Samples 25, 26, 27, 28, 37... Are 1 × 10 ¹⁸ cm ⁻³ on the F plane and 1 × 10 ¹⁵ cm ⁻³ on the C plane. Samples 29 and 30 are 5 × 10 ¹⁶ and 1 × 10 ¹⁷ cm ⁻³ on the F plane, and 1 × 10 ¹⁵ cm ⁻³ on the C plane. The C and F surfaces are in the same atmosphere. It is strange that the oxygen absorption on the C plane is 1 × 10 ¹⁵ cm ⁻³ even though the oxygen absorption on the F plane is 100 or 200 times different. The oxygen absorption on the C plane should be proportional to the oxygen absorption on the F plane.
The oxygen concentration of 1 × 10 ¹⁵ cm ⁻³ seems to be the limit of oxygen detection by this SIMS machine. All 1 × ¹⁰ 15 that's the amount of oxygen in ^{cm -3} will to display that it is 1 × ¹⁰ 15 ^{cm -3.} F surface is 1 × ¹⁰ 19 ^{cm -3,} when 1 × ¹⁰ 15 and ^{cm -3} is correct C-plane, the ratio is 10 ⁴ times. As shown by the broken line at 45 ° in FIG. 30, when the F-plane density is lower, there is probably a C-plane density at a position where the F-plane density point is lowered as shown by the arrow. If the F-plane oxygen concentration is 1 × 10 ¹⁸ cm ⁻³ for the samples 25, 26, 27..., The C-plane oxygen concentration is 1 × 10 ¹⁴ cm ⁻³ . Since it is below the detection limit, it may not be understood. The C-plane oxygen concentrations in Table 1 are all 1 × 10 ¹⁵ cm ⁻³ . It is not correct and below the limit, so it cannot be measured. This means that the C-plane oxygen concentration can be regarded as zero. The oxygen concentration in the C-plane growth region Y is zero. That is, O _C = [O] _y = 0.

For type II, there were four concentration parameters. These are the Si concentration on the C plane, the oxygen concentration on the C plane, the Si concentration on the F plane, and the oxygen concentration on the F plane. It was found that the oxygen concentration on the C plane was zero. It was found that O _C = 0 and the Si concentration in the F plane and C plane was equal (Si _C = Si _F ). This means that the number of free parameters is two. The oxygen concentration at the F plane is O _F = [O] _z , and the common Si concentration is Si _F = [Si] _z = Si _C = [Si] _y . This is simply written as [O], [Si]. In the case of type I, only [Si] exists because the surface is a C plane. That corresponds to white circles 1, 2, 3, 5, 8-19, and 22-24 in FIG. 27 localized at Si = 1 × 10 ¹⁸ cm ⁻³ and specific resistance r = 9 × 10 ⁻³ Ωcm. To do. Samples 20, 21, 4, and 7 are I type and have higher Si concentration and lower specific resistance. When these points are approximated by a straight line passing through points of Si = 1 × 10 ¹⁸ cm ⁻³ and r = 9 × 10 ⁻³ Ωcm, Si = 1 × 10 ¹⁹ cm ⁻³ and r = 4.4 × 10 ^−3. A one-dot chain line passing through Ωcm is obtained. When the relationship between the specific resistance r and the Si concentration is obtained as a straight line passing through these two points,
logr = 3.55-0.311 log [Si]
An approximate expression like this can be obtained for type I. . When the specific resistance unit is 1 × 10 ⁻³ Ωcm and expressed by r ′, r = r ′ × 10 ⁻³ . When the unit of Si concentration is 1 × 10 ¹⁸ cm ⁻³ and expressed by Si ′, it can be set as [Si ′] × 10 ¹⁸ = [Si]. Such a relationship between the specific resistance r ′ and the Si concentration Si ′ relates to the I type,
logr ′ = − 0.311 log [Si ′] + 0.954
And so on. This is an approximate expression of a broken line in FIG. Sample 7 (r ′ = 1.8, Si ′ = 50, Sample 6 (r ′ = 10, Si ′ = 0.1) deviates below the line. If the constant term is +0.689 or more, Sample 20 (r ′ = 7, Si ′ = 4), Sample 4 (r ′ = 4.7, Si ′ = 10) will fall above the line, which is a constant term of 1.032. It can be included if: The formula to include all type I samples is
0.689 ≦ logr ′ + 0.311 log [Si ′] ≦ 1.032
It looks like a dependency that is not inversely proportional to the first order of the Si concentration in a straight line but inversely proportional to the power of 0.311. I'm not sure it's not inversely proportional to the first power. As the Si concentration increases, the electron mobility decreases, which may be the effect. That is not clear. Still, the story is simpler because Type I has only Si on the surface.
The case of type II is more complicated. In FIG. 27, type II (white triangles) have different specific resistances even at the same Si concentration. Samples 25, 29, 30, 31, 32, 33, and 37 have [Si] = 1 × 10 ¹⁸ cm ⁻³ but different specific resistances. Samples 38, 26 and 34 have [Si] = 4 × 10 ¹⁸ cm ⁻³ but different specific resistance. The resistivity is not determined only by the Si concentration. Oxygen concentration becomes a problem.

FIG. 31 represents the oxygen concentration (cm ⁻³ ) and specific resistance (Ωcm) on the F plane in two-dimensional coordinates. Samples 33, 34, 35, and 36 having an oxygen concentration of 1 × 10 ¹⁹ cm ⁻³ have small specific resistances of 2 ×, 1.9 ×, 1.8 ×, and 1.5 × 10 ⁻³ Ωcm. A sample with a high oxygen concentration still gives the lowest specific resistance. Although oxygen is doped at a high concentration, the crack occurrence rate is 10, 11, 14, 18%, which is sufficiently lower than 22%. Differences in specific resistance and crack occurrence rate among the four samples are due to differences in Si concentration.
Samples 37, 25, 38, and 26 have an oxygen concentration of 1 × 10 ¹⁸ cm ⁻³ and a specific resistance of 6 to 8 × 10 ⁻³ Ωcm. The difference between them depends on the Si concentration. The Si concentration is 1 to 4 × 10 ¹⁸ cm ⁻³ . When the unit of the oxygen concentration is expressed as O ′ with 1 × 10 ¹⁸ cm ⁻³ and the coefficient of −0.311 of the I type is adopted,
logr ′ = − 0.311 log (1.6 [O ′] + [Si ′]) + 1.032
It becomes. This is true when the oxygen concentration is lower than 1 × 10 ¹⁸ cm ⁻³ .
Samples 33, 34, 35, and 36 have an oxygen concentration of 1 × 10 ¹⁹ cm ⁻³ . The Si concentration is [Si ′] = 1, 4, 7, and 10, and the specific resistance is r ′ = 2, 1.9, 1.8, and 1.5. If the coefficient of -0.311 is adopted,
logr ′ = − 0.311 log ([O ′] + [Si ′]) + 0.62. This is true when the oxygen concentration is higher than 1 × 10 ¹⁹ cm ⁻³ .
Thus, the formula containing all samples of type II is
logr ′ = − 0.311 log (κ [O ′] + [Si ′]) + S
However, κ = 1 to 1.6 and S = 0.62 to 1.032. This is a phenomenological formula and it may be considered that κ = 1.1, 1.3, 1.5. The coefficient is set to 0.311 for consistency with the I type. Considering type II, the coefficient may be changed between 0.3 and 0.5.
κ is a measure of the usefulness of Si and oxygen as dopants. κ = 1 means that both oxygen and silicon produce n-type carriers. κ = 1.6 means that silicon produces n-type carriers only 0.625 times oxygen.

FIG. 32 is a graph showing the value obtained by adding the F-plane oxygen concentration (cm ⁻³ ) to the C-plane silicon concentration (cm ⁻³ ) of the type II sample on the horizontal axis and the specific resistance (Ωcm) on the vertical axis. is there. That is, the horizontal axis is [Si] _C + [O] _F. This is because oxygen and Si are independent from each other, and each counts independently, and each of them produces n-type carriers. This is to examine the assumption. When the (Si + O) concentration of the sample and the specific resistance r are taken on the logarithmic graph paper in this way, it can be seen that the assumption is correct to some extent. Sample 36 is the sample having the lowest specific resistance doped with Si + O at the highest concentration. The presence of sample 36 supports the independent dopant assumption. That is not all. It can be seen that samples 35, 34, 39, 27, 26, and 38 are placed on the same straight null starting from sample 36. At the n point of the sample 36, Si + O = 20 × 10 ¹⁸ cm ⁻³ and r = 1.5 × 10 ⁻³ Ωcm. At the Lu point of the sample 26, Si + O = 5 × 10 ¹⁸ cm ⁻³ and r = 6 × 10 ⁻³ Ωcm. Similarly to the previous case, the concentration is expressed in units of 10 ¹⁸ cm ⁻³ and the specific resistance is expressed in units of 10 ⁻³ Ωcm.
Point [Si '] + [O'] = 20
r ′ = 1.5
Point [Si ′] + [O ′] = 5
r '= 6
A straight null is a right descending line of exactly 45 degrees. That is, a beautiful relationship is established that the specific resistance is inversely proportional to the total concentration of Si + O. The straight null formula is
logr ′ = 1.478−log {[Si ′] + [O ′]} (null)
It becomes. log represents a common logarithm. Expressed in the usual inverse proportion formula,
r ′ = 30 / {[Si ′] + [O ′]} (null ′)
This is a simple and easy-to-see expression. The fact that the coefficients of Si and O are equal means that the activation rates of Si and O are equal. A simple inverse proportionality means that a simple free electron model (Drude model) holds. 1 / r = σ = neμ. n is the n-type carrier concentration, e is the electronic charge, and μ is the mobility. Since the coefficients of Si and O are equal, if the activation rates ν of Si and O are substantially equal and ν _Si = ν _O = ν, the n-type carrier concentration n is n = ν {[Si] + [O]}. Become. Then
r = 1 / [eνμ {[Si] + [O]}]
It becomes. Since r = r ′ × 10 ⁻³ Ωcm, [Si] + [O] = {[Si ′] + [O ′]} × 10 ¹⁸ cm ⁻³ ,
r ′ × 10 ⁻³ = 1 / [eνμ {[Si ′] + [O ′]} × 10 ¹⁸ ]
If this and the above expression 'null' are equal,
^{eνμ = 10 3/30 × 10} 18 = 33 × 10 -18
It turns out that. e = 1.6 × 10 ⁻¹⁹ . Divide by this
νμ = 206 cm ² / Vs
And so on. With this amount of data, I don't know what ν is. If the activation rate is close to ν = 1, the mobility is 200 cm ² / Vs.
The equation that the product of the specific resistance r ′ and the concentration sum [Si ′] + [O ′] is 30 is an approximation that is good for the samples 36, 35, 34, 39, 27, 26, and 38 in FIG. is there. However, there are samples 25, 37, 31, 30, 29, 28, 33, etc. deviating from the straight line. For these samples as well, the specific resistance must be expressed as a function of the concentration sum. Sample 30 (point) is Si + O = 1.1 × 10 ¹⁸ cm ⁻³ and r = 7.9 × 10 ⁻³ Ωcm. Consider the equation of a straight line connecting the point (sample 36) and the point (sample 30).
Point [Si '] + [O'] = 20
r ′ = 1.5
W [Si '] + [O'] = 1.1
r ′ = 7.9
So the equation for the straight line is
logr ′ = 0.9213−0.5728 log {[Si ′] + [O ′]} (nuwo)
And so on. This should be displayed without logarithm,
r ′ = 8.334257 / {[Si ′] + [O ′]} ^0.5728
It turns out that.
Except for sample 32, the other type II is between a straight line and a straight line. In other words, a specific resistance determined by the following inequality is given.
0.9213-0.5728 log {[Si ′] + [O ′]} ≦ logr ′ ≦ 1.478−log {[Si ′] + [O ′]}
This can express the relationship between the concentration and specific resistance of all samples of type II except 32. Expressed in terms of power,
8.34257 / {[Si ′] + [O ′]} ^0.5728 ≦ r ′ ≦ 30 / {[Si ′] + [O ′]}
And so on. The fact that such a relationship holds with respect to type II suggests that Si and O do not interfere with each other and that n-type carriers are emitted one by one as donors. This means that the double doping of Si and O has favorable properties.

FIG. 3 is a plan view of an ELO mask in which a large number of small windows (exposed portions) are present at a narrow repetition pitch in a wide covering portion formed on a base substrate.

Process drawing for demonstrating the process of vapor-phase-growing a gallium nitride on the ELO mask on a base substrate.

The partial perspective view of the crystal | crystallization by the random facet growth method in which many facet pits from which a dimension differs on the crystal | crystallization surface generate | occur | produce at random.

In facet growth that maintains facet pits until the end of growth, the growth direction and dislocation direction are parallel, so the dislocations extend in the facet normal direction inside the facet pit, reach the facet boundary, descend along the boundary, and gather at the bottom of the pit The pit perspective view for explaining what to do.

In facet growth that maintains facet pits until the end of growth, the growth direction and dislocation direction are parallel, so the dislocations extend in the facet normal direction inside the facet pit, reach the facet boundary, descend along the boundary, and gather at the bottom of the pit The pit top view for demonstrating what to do.

FIG. 2 is a plan view of a part of a dot-type mask formed on a base substrate for maintaining facet pits until the end of growth, in which a large number of dot-shaped covering portions are regularly and vertically arranged at wide intervals.

The perspective view of the surface of the GaN crystal by the dot type facet growth method which produced the facet pit which has a bottom on the coating | coated part M by carrying out vapor phase growth of the GaN crystal on the base substrate which provided the dot type mask.

The top view of the GaN crystal by the dot type facet growth method which produced the facet pit which has a bottom on the coating | coated part M by carrying out the vapor phase growth of the GaN crystal on the base substrate which provided the dot type mask.

A vapor phase growth of a GaN crystal on a base substrate provided with a dot-type mask creates a facet pit with a bottom on the covering portion M, the facet pit becomes large, and a crystal defect gathering region H is generated on the mask. The longitudinal cross-sectional view for every process of the facet growth which shows the process of.

A plan view of a part of a striped mask formed on a base substrate and having a plurality of parallel line-shaped covering portions regularly and vertically with a wide interval in order to perform facet growth that maintains facet pits until the end of growth. .

A GaN crystal is vapor-phase-grown on a base substrate provided with a stripe-type mask, and a valley is present on the covering portion M, a flat top surface is present in the middle of the covering portion, and a facet inclined between the top surface and the valley exists. The top view of the GaN crystal by the stripe type facet growth method which produced many mountain valley structures.

A GaN crystal is vapor-phase-grown on a base substrate provided with a stripe-type mask, and a valley is present on the covering portion M, a flat top surface is present in the middle of the covering portion, and a facet inclined between the top surface and the valley exists. The perspective view of the GaN crystal by the stripe type facet growth method which produced many mountain valley structures.

A GaN crystal is vapor-phase-grown on a base substrate provided with a stripe mask, a valley is formed on the covering portion M, a sharp ridge line is present in the middle of the covering portion, and many facets are inclined between the sharp ridge line and the valley. The top view of the GaN crystal by the stripe type facet growth method which produced the mountain-valley structure.

A GaN crystal is vapor-phase-grown on a base substrate provided with a stripe mask, a valley is formed on the covering portion M, a sharp ridge line is present in the middle of the covering portion, and many facets are inclined between the sharp ridge line and the valley. The perspective view of the GaN crystal by the stripe-type facet growth method which created the mountain-valley structure.

When a stripe mask is formed on the base substrate and GaN is vapor-phase grown on the mask, the growth proceeds first in the exposed portion, so that a crystal having a C-face and a facet grows on the exposed portion, and is formed on the mask. FIG. 6 is a process cross-sectional view showing a process in which a low crystal defect gathering region H is formed, and a parallel mountain-valley structure is formed in which a valley is directly above the mask and a peak is in the middle of the mask.

FIG. 16 is a process cross-sectional view showing a process in which the crystal growth further progresses after FIG. 15 and the hills become higher and the valleys become larger in the stripe mask facet method.

Patent Document 7 (Patent No. 3826825) proposes that oxygen has little selectivity from the C-plane and is taken in a large amount through the facet, so that it grows in the c-axis direction by making facets. FIG. 3 is a cross-sectional view of a GaN crystal that can be doped with oxygen at a high concentration.

Patent Document 7 (Patent No. 3826825) proposes that oxygen has little selectivity from the C-plane and passes through facets and is taken in a large amount into the crystal, making crystals with surfaces other than the C-plane. FIG. 3 is a cross-sectional view of a GaN crystal in which oxygen can be doped at a high concentration by crystal growth of GaN thereon.

1 is a cross-sectional view of an HVPE furnace for producing the iron-doped nitride semiconductor crystal of the present invention.

Sectional drawing which shows the shape of the II type nitride semiconductor crystal with the mountain-valley structure produced by the method of this invention.

Sectional drawing which shows the shape of the I-type nitride semiconductor crystal with the flat surface produced by the method of this invention.

The graph which shows the growth temperature and 5/3 group ratio b as a coordinate for every Example in the vapor phase growth method of patent documents 1-11 which describe a prior art, and the vapor phase growth method of this invention. The horizontal axis is the growth temperature (° C.). The vertical axis represents the 5/3 group ratio b in logarithm.

The graph which showed the curvature radius (m) and crack generation rate (%) of the samples 1-45 which are the Example of this invention, and a comparative example by the point in the space which uses curvature and a crack as an abscissa. The number shaken is the sample number. White circles are type I, white triangles are type II, and x is a comparative example. Comparative examples are not known.

Sectional drawing which shows the shape of the mixed type nitride semiconductor crystal of I and II which has a facet part in the flat surface partly produced by the method of this invention.

The top view which shows the dimension of width | variety s of a stripe mask and the space | interval w in the method of this invention which forms the stripe mask which consists of several parallel coating | coated parts in a base substrate, and vapor-phase-grows a nitride semiconductor on it.

The top view which shows the dimension of the diameter s of a dot mask, and the dimension of the space | interval w in the method of this invention which forms the dot mask which consists of vertical and horizontal parallel several point-like covering part in a base substrate, and carries out vapor phase growth of the nitride semiconductor on it.

It is a graph which makes the logarithm of C surface part Si concentration (cm ^<-3 >) and the logarithm of specific resistance ((omega | ohm) cm) a horizontal-vertical coordinate, Comprising: All Si concentrations and specific resistances are represented by dots. The numbers are the sample numbers. White circles are type I, white triangles are type II, and x is a comparative example.

FIG. 2 is a graph having horizontal and vertical coordinates of type II F-plane Si concentration (cm ⁻³ ) and F-plane oxygen (O) concentration (cm ⁻³ ), and vapor phase growth of GaN described in the specification of the present invention All the Si concentration and O concentration of type II samples 25 to 39 are represented by dots. Sample points are indicated by white triangles. The numbers are the sample numbers.

Type II C surface Si concentration ^{(cm -3)} and F surface Si concentration ^{(cm -3)} A graph to coordinates of the horizontal and vertical, II-type GaN vapor deposition as described in the specification of the present invention All the Si concentrations of Samples 25 to 39 are represented by dots. Sample points are indicated by white triangles. The numbers are the sample numbers.

FIG. 2 is a graph in which the logarithm of the type II F-plane oxygen (O) concentration (cm ⁻³ ) and C-plane oxygen (O) concentration (cm ⁻³ ) logarithm is a horizontal and vertical coordinate, and is described in the specification of the present invention. All the O concentrations of type II samples 25 to 39 and comparative examples 44 to 45 of vapor phase growth of GaN are represented by dots. The numbers are the sample numbers. White triangles are type II, and x is a comparative example.

FIG. 11 is a graph in which the logarithm of the type II F-plane oxygen (O) concentration (cm ⁻³ ) logarithm and the specific resistance (Ωcm) is a horizontal and vertical coordinate, All oxygen concentrations and specific resistances of type II samples 25 to 39 are represented by dots. The numbers are the sample numbers. Sample points are indicated by white triangles.

11 is a graph in which the logarithm of the value obtained by adding the oxygen concentration of the F-plane to the silicon concentration of the II-type C-plane and the logarithm of the specific resistance (Ωcm) is expressed in the horizontal and vertical coordinates. All Si concentrations and specific resistances of Vapor growth type II samples 25 to 39 are represented by dots. The numbers are the sample numbers. Sample points are indicated by white triangles.

Explanation of symbols

U Underlying substrate
M Mask cover
E Exposed part not covered by mask
W ELO mask window
T dislocation
G crystal
F facet
C C side
P pit (facet pit)
V Growth direction (normal direction)
H Crystal defect assembly region (Closed defect assembly region)
Z Low defect single crystal region (Single crystal low dislocation associated region)
Y C-plane growth region (single crystal low dislocation residual region)
K grain boundary
s Diameter or width of mask cover
w Mask cover interval
p Repeat pitch of mask coating
2 Reactor
3 Heater
4 Ga reservoir
5 Susceptors
6 Base substrate
7 First source gas supply pipe
8 Second source gas supply pipe
9 Gas exhaust pipe
10 Third source gas supply pipe

Claims (36)

On a base substrate having a C-plane or a three-fold symmetry plane, a covering portion and a exposing portion having a width or diameter s of 10 μm to 100 μm and an interval w of 250 μm to 10000 μm are formed periodically. Is supplied from a Group 3 or Group 5 source gas and a silicon compound gas, water, or oxygen such that the 5/3 group ratio b is 1 to 10, and is on the base substrate. A nitride semiconductor crystal having a facet F on the surface is grown while doping silicon and oxygen, and a low-defect single crystal region Z following the facet F and a C-plane growth region Y following the flat surface are formed in the exposed portion. A crystal defect assembly region H is formed above, oxygen and silicon are doped through the facet F, and silicon is doped through the C plane to grow a nitride semiconductor crystal having a structure of HZYZHZYZ. After the growth, the base substrate is removed and the surface is polished to obtain a self-supporting n-type nitride semiconductor crystal having a crack occurrence rate K of 1% ≦ K ≦ 22%. Method. The substrate temperature is 1090 ° C. to 1150 ° C., the 5/3 group ratio b is 1 to 5, and growth is performed including facets at first, but the surface is finally covered with a flat C surface. The method for producing a conductive nitride semiconductor substrate according to claim 1, wherein an I-type crystal having a flat surface is grown. 3. The method for producing a conductive nitride semiconductor substrate according to claim 2, wherein the Si compound gas is supplied in the middle of the growth and the silicon doping is started in the middle without supplying the Si compound gas at the beginning of the growth. . 4. The method of manufacturing a conductive nitride semiconductor substrate according to claim 3, wherein the supply amount of the Si compound gas is increased so as to be maximized at the end of the growth. 3. The method for producing a conductive nitride semiconductor substrate according to claim 2, wherein the Si concentration on the C plane is 1 × 10 ¹⁷ cm ^{−3 to} 5 × 10 ¹⁹ cm ⁻³ . 4. The method for producing a conductive nitride semiconductor substrate according to claim 3, wherein a curvature radius of curvature after polishing is 3.5 m ≦ U ≦ 8 m. On the (111) GaAs base substrate, a stripe coating portion and an exposed portion having a width s of 50 μm, an interval w of 500 μm, and a period p of 550 μm are formed, and the substrate temperature is 1100 ° C. by HVPE, A Group 3 or Group 5 source gas having a Group 3 ratio b of 1 to 3 and a silicon compound gas, water or oxygen are supplied, and a nitride semiconductor crystal having a facet F on the surface of a base substrate is formed of silicon. And a low defect single crystal region Z following the facet F and a C-plane growth region Y following the flat surface in the exposed portion, and a crystal defect gathering region H on the covering portion. Oxygen and silicon are doped through facet F, and silicon is doped through the C plane, and a nitride semiconductor crystal having a structure of HZYZHZYZ... Is grown inside, finally forming a crystal covered with the C plane. The plate is removed, the surface is polished, and the rate of occurrence of crack K is 1% ≦ K ≦ 22%, the curvature radius U is 4 m ≦ U ≦ 8 m, and the specific resistance is 0.0018 Ωcm to 0.01 Ωcm. A method for producing a conductive nitride semiconductor substrate according to claim 2, wherein a type nitride semiconductor crystal is obtained. On the (111) GaAs base substrate, a dot covering portion and an exposed portion having a width s of 50 μm, an interval w of 500 μm, and a period p of 550 μm are formed, and the substrate temperature is 1100 ° C. by the HVPE method. A Group 3 or Group 5 source gas having a Group 3 ratio b of 2.5, a silicon compound gas, water, or oxygen is supplied, and a nitride semiconductor crystal having a facet F on the surface of a base substrate is formed of silicon. And a low defect single crystal region Z following the facet F and a C-plane growth region Y following the flat surface in the exposed portion, and a crystal defect gathering region H on the covering portion. Oxygen and silicon are doped through facet F, silicon is doped through C plane, and a nitride semiconductor crystal having a structure of HZYZHZYZ... Is grown inside, and finally a crystal covered with C plane is formed. After removing and polishing the surface, the crack occurrence rate K is 4% ≦ K ≦ 13%, the curvature radius U is 3.5 m ≦ U ≦ 4.8 m, and the specific resistance is 0.005 Ωcm to 0.009 Ωcm. The method for producing a conductive nitride semiconductor substrate according to claim 2, wherein an n-type nitride semiconductor crystal is obtained. When the specific resistance is expressed by r and the Si concentration is expressed by [Si],
logr = 3.55-0.311 log [Si]
3. The method of manufacturing a conductive nitride semiconductor substrate according to claim 2, wherein specific resistance is given by (log is a common logarithm). When the specific resistance r is expressed by r ′ × 10 ⁻³ Ωcm and the Si concentration [Si] is expressed by [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ ,
logr ′ = − 0.311 log [Si ′] + 0.954
3. The method of manufacturing a conductive nitride semiconductor substrate according to claim 2, wherein specific resistance is given by (log is a common logarithm). When the specific resistance r is expressed by r ′ × 10 ⁻³ Ωcm and the Si concentration [Si] is expressed by [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ ,
0.689 ≦ logr ′ + 0.311 log [Si ′] ≦ 1.032
3. The method of manufacturing a conductive nitride semiconductor substrate according to claim 2, wherein specific resistance is given by (log is a common logarithm). Type II with a substrate temperature of 1040 ° C. to 1070 ° C., a 5/3 group ratio b of 1 to 10, growth including facets from the beginning to the end, and a surface covered with facets of Yamaya The method for producing a conductive nitride semiconductor substrate according to claim 1, wherein crystals are grown. 13. The method for manufacturing a conductive nitride semiconductor substrate according to claim 12, wherein the supply of the silicon compound gas is increased as the growth proceeds. 13. The method for manufacturing a conductive nitride semiconductor substrate according to claim 12, wherein a curvature radius of curvature after polishing is 4.2 m ≦ U ≦ 6.5 m. On the (111) GaAs base substrate, a stripe coating portion and an exposed portion having a width s of 50 μm, a spacing w of 500 μm, and a period p of 550 μm are formed, and the substrate temperature is 1050 ° C. by the HVPE method. A Group 3 or Group 5 source gas having a Group 3 ratio b of 2.5, a silicon compound gas, water, or oxygen is supplied, and a nitride semiconductor crystal having a facet F on the surface of a base substrate is formed of silicon. And a low defect single crystal region Z following the facet F and a C-plane growth region Y following the flat surface in the exposed portion, and a crystal defect gathering region H on the covering portion. Oxygen and silicon are doped through the facet F, and silicon is doped through the C plane, and a nitride semiconductor crystal having a structure of HZYZHZYZ... Is grown inside, and the facet plane is maintained until the end. A II-type crystal covered with a plane and a part of the C plane is removed. After the growth, the base substrate is removed, the surface is polished, and the crack generation rate K is 5% ≦ K ≦ 18%, and the curvature radius U is 4.8 m ≦ 13. The method for producing a conductive nitride semiconductor substrate according to claim 12, wherein a self-standing n-type nitride semiconductor crystal having a specific resistance of 0.0015 Ωcm to 0.008 Ωcm is obtained when U ≦ 6.5 m. On the (111) GaAs base substrate, a dot covering portion and an exposed portion having a width s of 50 μm, an interval w of 500 μm, and a period p of 550 μm are formed, and the substrate temperature is 1050 ° C. by the HVPE method. A Group 3 or Group 5 source gas having a Group 3 ratio b of 2.5, a silicon compound gas, water, or oxygen is supplied, and a nitride semiconductor crystal having a facet F on the surface of a base substrate is formed of silicon. And a low defect single crystal region Z following the facet F and a C-plane growth region Y following the flat surface in the exposed portion, and a crystal defect gathering region H on the covering portion. Oxygen and silicon are doped through the facet F, and silicon is doped through the C plane, and a nitride semiconductor crystal having a structure of HZYZHZYZ ... is grown inside, and the facet plane is maintained until the end, and finally the facet plane A II-type crystal partially covered with a C-plane is formed. After the growth, the base substrate is removed, the surface is polished, the crack generation rate K is 3% ≦ K ≦ 6%, and the curvature radius U is 4.2 m ≦ U ≦ 13. The method for producing a conductive nitride semiconductor substrate according to claim 12, wherein a self-supporting n-type nitride semiconductor crystal having a specific resistance of 0.004 Ωcm to 0.008 Ωcm at 5 m is obtained. Specific resistance r is r ′ × 10 ⁻³ Ωcm, Si concentration [Si] is [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ , and oxygen concentration [O] is [O ′] × 10 ¹⁸ cm ⁻³ . When expressed
logr ′ = − 0.311 log (1.6 [O ′] + [Si ′]) + 1.032
The method of manufacturing a conductive nitride semiconductor substrate according to claim 12, wherein the specific resistance is expressed by: Specific resistance r is r ′ × 10 ⁻³ Ωcm, Si concentration [Si] is [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ , and oxygen concentration [O] is [O ′] × 10 ¹⁸ cm ⁻³ . When expressed
logr ′ = − 0.311 log ([O ′] + [Si ′]) + 0.62
The method of manufacturing a conductive nitride semiconductor substrate according to claim 12, wherein the specific resistance is expressed by: Specific resistance r is r ′ × 10 ⁻³ Ωcm, Si concentration [Si] is [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ , and oxygen concentration [O] is [O ′] × 10 ¹⁸ cm ⁻³ . When expressed
logr ′ = − 0.311 log (κ [O ′] + [Si ′]) + S
13. The method of manufacturing a conductive nitride semiconductor substrate according to claim 12, wherein the specific resistance is expressed by (where κ = 1 to 1.6, S = 0.62 to 1.032). A crystal defect assembly region H having a width or diameter of 10 μm to 100 μm and a low defect single crystal region Z, a C-plane growth region Y, and a low defect single crystal region Z between the crystal defect assembly regions H and H, 250 μm to 10,000 μm. HZYZHZYZ... In which ZYZ of a width of N is repeated periodically holds the structure at the bottom and inside, the surface has only the C-plane growth region Y, and the low defect single crystal region Z and the crystal defect assembly region H include silicon and oxygen. The C-plane growth region Y is doped with silicon, the thickness is 100 μm or more, the diameter is 18 mm or more, the crack generation rate K is 1% ≦ K ≦ 22%, and the curvature radius of warpage A conductive nitride semiconductor substrate, wherein U is 3.5 m ≦ U ≦ 8 m, and the specific resistance r is 0.0015 Ωcm ≦ r ≦ 0.01 Ωcm. A crystal defect assembly region H having a width or diameter of 10 μm to 100 μm and a low defect single crystal region Z, a C-plane growth region Y, and a low defect single crystal region Z between the crystal defect assembly regions H and H, 250 μm to 10,000 μm. HZYZHZYZ... In which ZYZ of a width of N is repeated periodically holds the structure at the bottom and inside, the surface has only the C-plane growth region Y, and the low defect single crystal region Z and the crystal defect assembly region H include silicon and oxygen. The C-plane growth region Y is doped with silicon, the thickness is 100 μm or more, the diameter is 18 mm or more, the crack generation rate K is 1% ≦ K ≦ 22%, and the curvature radius of warpage 21. The conductive nitride semiconductor substrate according to claim 20, wherein U is 3.5 m ≦ U ≦ 8 m and the specific resistance r is 0.0018 Ωcm ≦ r ≦ 0.01 Ωcm. A parallel linear crystal defect collecting region H having a width of 10 μm to 100 μm, and a parallel linear low defect single crystal region Z, a C-plane growth region Y, and a low defect single crystal region Z between the crystal defect collecting regions H and H. Striped HZYZHZYZ in which ZYZ having a width of 250 μm to 10000 μm is repeated and the structure is periodically held at the bottom and inside, the surface has only the C-plane growth region Y, and the low defect single crystal region Z and the crystal defect collection The region H is doped with silicon and oxygen, and the C-plane growth region Y is doped with silicon. The thickness is 100 μm or more, the diameter is 18 mm or more, and the crack occurrence rate K is 1% ≦ K ≦ 22%. 21. The conductive nitriding according to claim 20, wherein a curvature radius U of warpage is 4.0 m ≦ U ≦ 8 m, and a specific resistance r is 0.0018 Ωcm ≦ r ≦ 0.01 Ωcm. A semiconductor substrate. It consists of a point-like crystal defect assembly region H having a diameter of 10 μm to 100 μm, and a low defect single crystal region Z, a C-plane growth region Y, and a low defect single crystal region Z between and surrounding the crystal defect assembly regions H, H. A dot-like HZYZHZYZ in which ZYZ with a width of 250 μm to 10000 μm is repeated is periodically held at the bottom and inside, the surface has only a C-plane growth region Y, a low defect single crystal region Z and a crystal defect gathering region H Is doped with silicon and oxygen, the C-plane growth region Y is doped with silicon, the thickness is 100 μm or more, the diameter is 18 mm or more, and the crack occurrence rate K is 4% ≦ K ≦ 13%. 21. The conductive nitride according to claim 20, wherein a curvature radius U of warpage is 3.5 m ≦ U ≦ 4.8 m, and a specific resistance r is 0.005 Ωcm ≦ r ≦ 0.009 Ωcm. Half Body board. When the specific resistance is expressed by r and the Si concentration by [Si]
logr = 3.55-0.311 log [Si]
The conductive nitride semiconductor substrate according to claim 21, wherein a specific resistance is given by (log is a common logarithm). When the specific resistance r is expressed by r ′ × 10 ⁻³ Ωcm and the Si concentration [Si] is expressed by [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ ,
logr ′ = − 0.311 log [Si ′] + 0.954
The conductive nitride semiconductor substrate according to claim 21, wherein a specific resistance is given by (log is a common logarithm). When the specific resistance r is expressed by r ′ × 10 ⁻³ Ωcm and the Si concentration [Si] is expressed by [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ ,
0.689 ≦ logr ′ + 0.311 log [Si ′] ≦ 1.032
The conductive nitride semiconductor substrate according to claim 21, wherein a specific resistance is given by (log is a common logarithm). A crystal defect assembly region H having a width or diameter of 10 μm to 100 μm and a low defect single crystal region Z, a C-plane growth region Y, and a low defect single crystal region Z between the crystal defect assembly regions H and H, 250 μm to 10,000 μm. HZYZHZYZ... In which ZYZ of a width of N is repeated periodically holds the structure at the bottom and inside, the surface has only the C-plane growth region Y, and the low defect single crystal region Z and the crystal defect assembly region H include silicon and oxygen. The C-plane growth region Y is doped with silicon, the thickness is 100 μm or more, the diameter is 18 mm or more, the crack generation rate K is 3% ≦ K ≦ 18%, and the curvature radius of warpage 21. The conductive nitride semiconductor substrate according to claim 20, wherein U is 4.2 m ≦ U ≦ 6.5 m, and the specific resistance r is 0.0015 Ωcm ≦ r ≦ 0.008 Ωcm. A parallel linear crystal defect collecting region H having a width of 10 μm to 100 μm, and a parallel linear low defect single crystal region Z, a C-plane growth region Y, and a low defect single crystal region Z between the crystal defect collecting regions H and H. The stripe-shaped HZYZHZYZ... Structure in which ZYZ having a width of 250 μm to 10000 μm is repeated periodically holds the structure, the low-defect single crystal region Z and the crystal defect assembly region H are doped with silicon and oxygen, and the C-plane growth region Y Is doped with silicon, has a thickness of 100 μm or more, a diameter of 18 mm or more, a crack generation rate K of 5% ≦ K ≦ 18%, and a curvature radius U of warpage is 4.8 m ≦ U ≦ 6. 21. The conductive nitride semiconductor substrate according to claim 20, wherein the resistivity r is 0.0015 Ωcm ≦ r ≦ 0.008 Ωcm. It consists of a point-like crystal defect assembly region H having a diameter of 10 μm to 100 μm, and a low defect single crystal region Z, a C-plane growth region Y, and a low defect single crystal region Z between and surrounding the crystal defect assembly regions H, H. The dot-like HZYZHZYZ in which ZYZ with a width of 250 μm to 10000 μm is repeatedly held periodically, the low-defect single crystal region Z and the crystal defect assembly region H are doped with silicon and oxygen, and the C-plane growth region Y Silicon is doped, the thickness is 100 μm or more, the diameter is 18 mm or more, the crack occurrence rate K is 3% ≦ K ≦ 6%, and the curvature radius U of warping is 4.2 m ≦ U ≦ 5 m. 21. The conductive nitride semiconductor substrate according to claim 20, wherein a specific resistance r is 0.004 Ωcm ≦ r ≦ 0.008 Ωcm. Specific resistance r is r ′ × 10 ⁻³ Ωcm, Si concentration [Si] is [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ , and oxygen concentration [O] is [O ′] × 10 ¹⁸ cm ⁻³ . When expressed
logr ′ = − 0.311 log (1.6 [O ′] + [Si ′]) + 1.032
28. The conductive nitride semiconductor substrate according to claim 27, wherein a specific resistance is expressed by: Specific resistance r is r ′ × 10 ⁻³ Ωcm, Si concentration [Si] is [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ , and oxygen concentration [O] is [O ′] × 10 ¹⁸ cm ⁻³ . When expressed
logr ′ = − 0.311 log ([O ′] + [Si ′]) + 0.62
28. The conductive nitride semiconductor substrate according to claim 27, wherein a specific resistance is expressed by: Specific resistance r is r ′ × 10 ⁻³ Ωcm, Si concentration [Si] is [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ , and oxygen concentration [O] is [O ′] × 10 ¹⁸ cm ⁻³ . When expressed
logr ′ = − 0.311 log (κ [O ′] + [Si ′]) + S
28. The conductive nitride semiconductor substrate according to claim 27, wherein the specific resistance is expressed by (where κ = 1 to 1.6, S = 0.62 to 1.032). Specific resistance r is r ′ × 10 ⁻³ Ωcm, Si concentration [Si] is [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ , and oxygen concentration [O] is [O ′] × 10 ¹⁸ cm ⁻³ . When expressed
logr ′ = 1.478−log {[Si ′] + [O ′]}
28. The conductive nitride semiconductor substrate according to claim 27, wherein a specific resistance is expressed by: Specific resistance r is r ′ × 10 ⁻³ Ωcm, Si concentration [Si] is [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ , and oxygen concentration [O] is [O ′] × 10 ¹⁸ cm ⁻³ . When expressed
r ′ = 30 / {[Si ′] + [O ′]}
28. The conductive nitride semiconductor substrate according to claim 27, wherein a specific resistance is expressed by: Specific resistance r is r ′ × 10 ⁻³ Ωcm, Si concentration [Si] is [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ , and oxygen concentration [O] is [O ′] × 10 ¹⁸ cm ⁻³ . When expressed
0.9213-0.5728 log {[Si ′] + [O ′]} ≦ logr ′ ≦ 1.478−log {[Si ′] + [O ′]}
28. The conductive nitride semiconductor substrate according to claim 27, wherein a specific resistance is expressed by: Specific resistance r is r ′ × 10 ⁻³ Ωcm, Si concentration [Si] is [Si] = [Si ′] × 10 ¹⁸ cm ⁻³ , and oxygen concentration [O] is [O ′] × 10 ¹⁸ cm ⁻³ . When expressed
8.34257 / {[Si ′] + [O ′]} ^0.5728 ≦ r ′ ≦ 30 / {[Si ′] + [O ′]}
28. The conductive nitride semiconductor substrate according to claim 27, wherein a specific resistance is expressed by:

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