JP4656438B2 - Single crystal GaN substrate manufacturing method and single crystal GaN substrate - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a single crystal GaN substrate used for a light emitting device such as a light emitting diode (LED) or a semiconductor laser (LD) made of a group 3-5 nitride compound semiconductor, and a single crystal GaN substrate obtained thereby. .

Light emitting devices using nitride-based semiconductors have already been put into practical use for blue LEDs. Conventionally, most light emitting devices using nitride-based semiconductors use sapphire (Al ₂ O ₃ ) as a substrate. A GaN or GaInN thin film was epitaxially grown on the sapphire substrate. Sapphire is a very stable substrate material suitable for GaN growth. This is an excellent point of sapphire.

  But sapphire is a very hard material. Moreover, there is no convenient cleavage when making a resonator with an LD. Since it does not cleave naturally, the wafer must be mechanically cut into chips. In the light emitting diode manufacturing process, there is a drawback that the dicing process increases the cost. In the production of semiconductor lasers, a reflective surface (resonator) cannot be produced by cleaving, resulting in quality problems and high costs.

  Sapphire is an insulating substrate. An LED using a sapphire as a substrate cannot take electrodes on the top and bottom of the device, unlike a normal LED. Also in terms of process, it is necessary to remove a part of the chip by etching and to provide a surface by exposing the lower layer portion to produce a device. Further, after etching, it is necessary to grow a relatively thick conductive layer for passing a current in the lateral direction. These processes increase the number of processes and process time, resulting in high costs. Furthermore, it is necessary to form two electrodes on the same surface, and a large chip area is required. This also led to an increase in cost.

  Since sapphire substrates have such difficulties, the possibility of using SiC substrates as substrates for GaN-based light emitting devices has been proposed. SiC has a cleavage property. Dividing the LED into chips is facilitated by natural cleavage. A semiconductor laser resonator can be formed by natural cleavage. Moreover, since it is conductive, the electrodes can be distributed above and below the chip. So it is more convenient in terms of process. However, SiC substrates are very expensive. The production volume is small and there are difficulties in supply. Furthermore, the SiC substrate has a problem in crystal quality and is not optimal as a substrate for a GaN-based semiconductor.

As with sapphire, when a heterogeneous substrate such as SiC is used, there is a problem that a mismatch of lattice constant between GaN and the substrate material introduces many defects such as dislocations in the epitaxial layer. It is said that a large number of dislocations of about 1 × 10 ⁹ cm ⁻² are present in a GaN epitaxial layer of a device using a sapphire substrate that is currently commercially available.

Although the dislocation density is somewhat smaller than that of sapphire, it is said that there are dislocations of about 1 × 10 ⁸ cm ⁻² or more when using a SiC substrate. A large amount of dislocations does not hinder the practical application of LEDs. However, in the case of a semiconductor laser (LD) having a remarkably large current density, it has become clear that these defects cause an increase in the life of the semiconductor laser.
For these reasons, it can be seen that sapphire substrates and SiC substrates are still not optimal as substrates for blue light emitting elements (LEDs, LDs).

  The most ideal substrate is a GaN single crystal. If a GaN single crystal substrate is obtained, the problem of crystal lattice mismatch is completely eliminated. Moreover, GaN has a cleavage property and can also be conductive. It should be very convenient. However, the crystal production technology is still not mature. It is difficult to manufacture a GaN single crystal substrate having a practical size that can be used as a substrate for device manufacturing.

  It is said that GaN crystals can be synthesized under ultra-high pressure while maintaining an equilibrium state. However, large GaN crystals cannot be synthesized under ultra high pressure. Therefore, this method cannot make a large GaN substrate. Commercial GaN substrate supply is not feasible with this method.

  As a result of examining the above technical problems, a method for reducing dislocation defects by vapor-phase growth of GaN on a sapphire substrate through a mask layer with a window has been proposed. (Non-patent document 1, Non-patent document 2)

  Furthermore, the present inventor has already invented a method for obtaining a GaN substrate by vapor-phase growth of GaN on a GaAs substrate through a mask layer with a window. (Patent Document 1 and Patent Document 2)

  According to this, it can be said that a GaN crystal having a relatively low crystal defect density and a large area can be grown. This is called “Epitaxial Lateral Overgrowth (ELO)”. This is simply called the lateral growth method.

  Specifically, a GaN substrate is formed by forming a mask having a large number of stripe windows and circular windows on a GaAs substrate by a vapor phase synthesis method such as HVPE, laterally growing GaN on the mask, and then removing the GaAs substrate. It is a method of getting.

The HVPE method will be described with reference to FIG. A Ga boat 2 is provided above the inside of the vertically long furnace 1. This contains Ga melt 3. A susceptor 4 is provided below the furnace 1 so as to be rotatable up and down. A GaAs substrate 5 is placed on the susceptor 4. There is a heater 6 around the furnace 1 to heat the furnace 1. A mixed gas of hydrogen gas and HCl gas is introduced from a gas inlet 7 located above the furnace 1. HCl reacts with Ga to synthesize GaCl, and GaCl becomes gaseous and flows downward. A mixed gas of hydrogen gas and NH ₃ gas is introduced from the gas inlet 8. This reacts with GaCl to synthesize GaN and deposit it on the GaAs substrate 5. The exhaust gas is removed from the gas outlet 9.

The lateral growth method will be described with reference to FIGS. This is described in detail in Patent Document 1 and Patent Document 2. A mask with a window is formed on the GaAs (111) substrate, and GaN is epitaxially grown through the window. FIG. 2 is a plan view of a mask having a square window formed on a GaAs substrate. The entire surface of the GaAs wafer (substrate) 10 is covered with a thin mask 11. The mask 11 is made of a material that does not allow GaN to grow directly on it. The windows 11 are regularly opened in the mask 11. The windows are provided at positions where three adjacent windows form an equilateral triangle. The windows are arranged at intervals L in a certain direction. The interval between adjacent columns is 3 ^1/2 L / 2, and the windows of adjacent columns are shifted in the column direction by L / 2. This is a square window, but a round window may be provided.

  FIG. 3 shows a mask with a striped window opened. This is also the same as the previous example, in which a mask 11 on which GaN does not grow is coated on a GaAs substrate 10 and a window 12 is provided at the apex of an equilateral triangle. The difference is the shape of the window. This is a mask that opens a rectangular window. This is called a striped window.

  After attaching such a mask, GaN is grown on the GaAs wafer 10 by the aforementioned HVPE method or the like. FIG. 4 shows how GaN is deposited on a GaAs substrate. FIG. 4A shows a cross section of the GaAs substrate 10 provided with the mask 11. It is a state before growth. When GaN is synthesized, a GaN layer grows selectively only in the window portion where GaAs is exposed. The mask has an effect of inhibiting the growth of GaN and cannot grow on it. When growing higher than the height of the mask 11 as shown in FIG. 4B, a pyramidal GaN raised portion 13 is formed. This is a pyramid with a {11-22} plane.

  The thin line indicates threading dislocations 14. As the layer grows, the dislocations 14 extend in the growth direction. Dislocations are called threading dislocations because they extend through the stacking layers. The threading dislocation 14 extends upward. The crystal orientation is determined by the underlying GaAs, but the mask row direction is [10-10] and the direction perpendicular to the mask row is the [1-210] direction. The direction of growth is [0001], which is c-axis growth.

  If the layer becomes thicker than that, it will protrude onto the mask. The inclined surface that appears preferentially is the {11-22} plane. It is called a faceted surface because it has a clear surface index that is not parallel to the substrate surface. This is as shown in FIG. This is because GaN is grown horizontally from the side of the GaN raised layer 13 instead of growing on the mask. During this time, the height of the horizontal extension layer 15 is constant for a while. Since it grows beyond the mask 11, it is named overgrowth. The threading dislocation 14 also extends laterally.

  It is reported by Non-Patent Document 1 and Non-Patent Document 2 that threading dislocations are very small in the portion that protrudes laterally from the window and grows on the mask. Usually, when growing in the c-axis direction, dislocations also extend in the c-axis direction. However, after growing in the vertical direction (c-axis direction) from the mask window, the direction of dislocation is changed from the vertical direction to the horizontal direction when growing in the lateral direction, and in particular in the region grown in the lateral direction, the C plane (0001). Non-Patent Document 1 and Non-Patent Document 2 claim that threading dislocations in the vertical direction are reduced.

  Eventually, the facet 16 {11-22} plane of the GaN horizontal extension layer 15 collides at the midpoint between the window and the adjacent window. Furthermore, the horizontal extension layer generated from the adjacent window is united by lateral growth. By merging, {11-22} facet surface 16 disappears. A planar defect portion 17 in which dislocations are accumulated is formed in the merged portion. After the facet plane 16 disappears, two-dimensional growth is performed on the C plane (0001) plane, and specular growth proceeds. Thereafter, the GaN layer 18 grows upward. Narrow threading dislocations begin to extend upward again. This threading dislocation will be described again later.

  It has also been reported that the planar defects 16 disappear when the upward (c-axis direction) epitaxial growth proceeds and the film thickness increases to about 140 μm (Non-patent Documents 1 and 2).

  FIG. 5 illustrates the same GaN layer growth. FIG. 5A shows a state in which the windowed mask 11 is formed on the GaAs substrate (111) 10. When the epitaxial growth of GaN is continued for a long time, the GaN ingot 18 grows greatly exceeding the height of the mask 11. This is the state shown in FIG. The growth direction is the [0001] direction, and the upper surface is the (0001) plane, that is, the C plane. The upper surface has a flat portion, but may have some unevenness. When the thick GaN ingot 18 can be grown, the GaAs substrate 10 and the mask 11 are removed from the furnace. A large number of GaN wafers (substrates) having the C plane as a surface are obtained by slicing the ingot 18 parallel to the C plane (growth plane). Further, the wafer is ground and polished to obtain a mirror wafer 19. These wafers are C-plane wafers. Since the cleavage plane is orthogonal to the C plane, it is advantageous for chip cutting and LD resonator fabrication.

  The method of FIG. 5 is to make a GaN wafer directly from a GaAs substrate, but there is another method.

Patent Document 3 is a method of mass-producing a GaN substrate (wafer) by making a GaN ingot by further growing a GaN crystal by the HVPE method or the like using the GaN substrate 19 manufactured in the process of FIG. is there. In this method, GaN is grown on the C-plane seed crystal in the c-axis direction [0001] to obtain an ingot, which is cut in parallel to the (0001) plane to obtain a C-plane wafer.

  These new methods of the inventor made it possible for the first time to produce GaN single crystal substrates on a commercial basis.

  There was still a problem with the GaN substrate thus fabricated. The biggest problem was that threading dislocations remained on the substrate surface. When the growth surface grows in a planar shape, threading dislocations extend perpendicular to the crystal surface without disappearing. As the crystal layer grows, the threading dislocation itself grows in the vertical direction. As a result, there are always threading dislocations on the growth surface.

In normal lateral overgrowth, at the initial stage of growth when the growth direction is changed to the horizontal direction, a region with little threading dislocations is formed in the growth portion on the mask (FIG. 4 (4)).
That's fine, but it's not a low dislocation. Further, when the growth is thick and tens of μm or more upward, the threading dislocations turn upward in the extension direction. When the thickness is 140 μm, the planar defect 17 disappears. That is, the aggregated threading dislocations are dispersed and work to increase the number. Therefore, dislocations spread with increasing epilayer thickness. Although the surface is a flat mirror surface, the dislocation density increases.

When the thickness of the laminated portion is several cm, a dislocation group having a large threading dislocation density of about 1 × 10 ⁷ cm ⁻² usually exists on the surface. The dislocation density once decreased due to the dislocation direction being laterally grown becomes the vertical growth, and the dislocation increases again as the film thickness increases. When a laser is formed by epitaxial growth on a GaN substrate having such a high dislocation density, deterioration proceeds from the dislocation and it is difficult to extend the life.

  Therefore, the present inventor has examined such a growth mode in detail. In the following description, in order to distinguish between a flat (0001) plane appearing in normal c-axis direction epi growth, that is, two-dimensional growth on the C plane and growth having an inclined plane, facet planes other than the C plane are used as ends. It is called the facet plane and the C plane is the growth plane. As shown in FIG. 4 (4), the facet plane {11-22} planes are combined on the mask with a film thickness of about 6 μm. Here, the dislocation density decreases. Combine and grow while maintaining the flat growth surface (C surface) as a mirror surface. The final film thickness was 0.2 mm to 0.6 mm, and the dislocation density was measured for each sample.

Although the dislocation density decreased due to the lateral overgrowth, it still exceeds 1 × 10 ⁷ cm ⁻² . The cause of this is thought to be that the dislocation density decreases once aggregated at the merged portion (FIG. 4 (4)) on the mask, but as the film thickness increases, the dislocation bundles become scattered and the dislocation density increases again. It is done.

  As long as the growth is two-dimensional (maintaining the mirror surface), the dislocation continues to extend in the c-axis direction. Dislocations once generated do not disappear. There is no dislocation annihilation mechanism in two-dimensional growth. Therefore, it was necessary to develop a method for eliminating dislocations actively. Is it possible for the present inventor to grow a crystal with a dislocation elimination mechanism provided in the crystal? I thought. As a result, the following invention has been conceived.

  In Patent Document 4, in order to reduce dislocations in a GaN substrate, the growth surface is not in a planar state (mirror surface), but a three-dimensional facet structure is formed, and growth is performed without embedding the facet structure. . By growing without embedding facets, particularly by forming facet pits, this is a clever growth method that concentrates dislocations in the pits and lowers the overall dislocations.

  In the present invention, a facet structure is provided on the GaN surface, dislocations are moved by lateral growth using the facet surface, and the dislocations are collected, for example, at the core of the pit bottom. Thereby, the entire crystal is lowered in dislocation. This is a truly clever method that reduces the apparent dislocation density by bundling dislocations together. Although the dislocations themselves do not disappear, the dislocation density seems to be significantly reduced because they are aggregated.

I will leave the explanation of the prior art for a while.
[Specify crystal orientation]
GaN is a hexagonal system, and the crystal orientation designation method is somewhat difficult. The present invention uses several expressions for hexagonal orientations. There should be no confusion. Here, the crystal orientation will be briefly described. In the case of the hexagonal system, two of the three axes forming 120 degrees are called an a axis and a b axis, and an axis orthogonal to these axes is called a c axis. Since the three axes are equivalent axes, the remaining axes will be referred to as, for example, the d-axis here. There are expression methods using three surface indices and expression methods using four surface indices. Here, the expression with a four-plane index is used. The a-axis length is a, and the c-axis length is c. The ratio of a / c varies depending on the substance even in the hexagonal system.

  Describe the definition of face index. When the first crystal plane closest to the origin cuts three equivalent axes a, b, and d with a / h, b / k, and d / m, and the c axis with c / n, the plane index is ( hkmn). The indices h, k, m, and n are integers. When expressing the face index, do not put a comma in parentheses. FIG. 6 shows the definition of the plane index in the abd plane. Here, the surface is cut along the a-axis and the b-axis on the positive half line, and the d-axis is cut on the negative half line. As can be seen in this figure, h, k, and m are not all positive and all negative.

Round brackets (...) are representations of individual surfaces. Curly brackets {····} are expressions of the collective surface. All of the individual planes that can be converted into each other by all of the symmetry operations of the hexagonal crystal can be expressed by the plane index of the collective expression. Square brackets [...] indicate individual orientations. Square brackets <...... represent a collective orientation. The plane and orientation with the same plane index are always orthogonal.
When {hkmn} is written, n is a unique direction (c-axis direction), but the previous three hkms are interchangeable. Crystals have 6-fold symmetry, and some crystals have inversion symmetry. {hkmn}, {kmhn}, {mhkn},..., in which h, k, and m are exchanged cyclically represent the same set of surfaces. However, n is unique and no longer has a different plane orientation when moved cyclically. h, k, m and n can be considered separately.

  In addition, the surface indices h, k, and m in the same plane can be expressed by two indices and are not completely independent. There is always a property that the sum is zero.

                  h + k + m = 0 (1)

  This is proved by FIG. O is the origin, and OB and OD are points on the b-axis and d-axis, and OB = OD. OH is the intersection of the -a axis and BD. ∠OBH = ∠ODH = 30 °. Let E and F be the intersections of a straight line passing through H and OB and OD. EHF expresses the surface. OE = Y, OF = Z, and OH = −X (−X> 0). ∠ DHF = θ. ∠OFH = 30 ° −θ, ∠OEH = 30 ° + θ, ∠OHF = 90 ° + θ, ∠OHE = 90 ° −θ. From the sine theorem

-X = Ysin∠OEH / sin∠OHE
= Ysin (30 ° + θ) / sin (90 ° -θ)
-X = Zsin∠OFH / sin∠OHF
= Zsin (30 ° -θ) / sin (90 ° + θ)

Because

−X / Y−X / Z = sin (30 ° + θ) / sin (90 ° −θ)
+ Sin (30 ° -θ) / sin (90 ° + θ)
= {Sin (30 ° + θ) + sin (30 ° −θ)} / cos θ
= 2sin30 ° = 1

And
1 / X + 1 / Y + 1 / Z = 0
It becomes. X = a / h, Y = b / k, Z = d / m, but regarding length, a = b = d,

          h + k + m = 0

It is.
For simplicity, consider a plane (n = 0) parallel to the c-axis. The surface interval d of the surface {hkm0} is

Given by. Although h, k, and m are two-dimensional exponents, they are shaped like a three-dimensional exponent. However, the point to which coefficient (3/2) ^1/2 is attached is different from the case of three-dimensional.
When there are two planes (hkm0) and (stu0) parallel to the c-axis, the cosine cosΘ of the angle (intersection angle) Θ between these planes is

によって計算することができる。つまりｃ軸に平行な二つの面（ｈｋｍ０）、（ｓｔｕ０）があってそれらが互いに直交する場合、

Can be calculated by: That is, if there are two planes (hkm0) and (stu0) parallel to the c-axis and they are orthogonal to each other,

                hs + kt + mu = 0 (4)

It is that.

  A plane (000n) whose normal is parallel to the c-axis is expressed as a C plane. The (hkm0) plane defined by all integers is orthogonal to the C plane. The surfaces orthogonal to each other in the surface group (hkm0) orthogonal to the C surface satisfy Expression (4). When the face index is a negative integer, it is a custom of crystallography to express that it is negative by overlining the number. However, since the specification cannot be overlined, it is preceded by a minus sign to indicate a negative integer.

  As shown in FIG. 8, the (1-100) plane and the (11-20) plane are orthogonal to each other. These two aspects have an important role in the present invention. The {1-100} plane is collectively referred to as the M plane. The {11-20} plane is collectively referred to as the A plane. Even though it is called the M plane, there are six individual planes. (1-100), (10-10), (01-10), (-1100), (-1010), (0-110). These surfaces can be arranged to form six sides of a regular hexagon. Therefore, the adjacent M planes form an angle of 120 degrees. Some M-planes are parallel (180 degrees), others have an angle of 120 degrees and an angle of 60 degrees. A regular hexagon can be formed only by the M plane.

  Similarly, the A plane {11-20} has six individual planes that are parallel to each other (180 degrees), 120 degrees, and 60 degrees. A regular hexagon can be created only from the set of A faces.

  Not all of the M and A planes are orthogonal, but a special set of M and A planes such as (1-100) and (11-20) planes are orthogonal. In general, the angles formed by the M plane and the A plane are 30 degrees, 90 degrees, 150 degrees, 210 degrees, 270 degrees, and 330 degrees.

That is, a regular dodecagon can be formed by six A planes and six M planes. A set of planes {11-2n} in which the A plane is inclined with respect to the c-axis can form a regular hexagonal pyramid. A set of planes {1-10n} in which the M plane is inclined with respect to the c-axis can form a regular hexagonal pyramid. A set of {11-2n} and {1-10n} in which the A plane and the M plane are inclined can form a regular 12 pyramid.
Akira Sakurai “Growth of thick GaN crystals by hydride VPE”, IEICE Transactions vol. J81-C-II, No. 1, p58-64 (January 1998) Akira Sakai, Akira Sakurai “Reduction of dislocation density by lateral growth of GaN” Applied Physics Vol.68, No.7, p774-779 (1999) Japanese Patent Application No. 9-298300 Japanese Patent Application No. 10-9008 Japanese Patent Application No. 10-102546 Japanese Patent Application No. 11-273882

  The inventor stated that Patent Document 4 proposed a growth method for reducing dislocations by growing GaN while generating and holding facet planes. However, according to this method, the concentration of dislocations occurs in the portion that hits the bottom of the faceted pit. As a result, a bundle of high-density dislocation portions is present continuously in a three-dimensional manner below the portion corresponding to the pit bottom. In other parts, there are good regions with low dislocations.

Although having such a merit that a low dislocation region exists in such a large area, a region where high density dislocations exist locally remains. For this reason, as already described, the device characteristics are lowered and the product yield is lowered. Moreover, it becomes a factor of cleaving inhibition.
In order to solve these problems, it is necessary to fundamentally reduce the threading dislocation density and eliminate the presence of dislocation bundles on the substrate surface.

  When the growth surface grows with pits made of facets instead of being flat, there is a bundle of threading dislocations made up of dislocation bundles in the direction perpendicular to the average growth surface at the bottom of the pits.

  As a result, in a region where threading dislocations exist, dislocations are concentrated in a narrow area. If the laser device structure is fabricated on the GaN substrate, a laser device with a short lifespan is produced at a limited rate.

  Another serious problem is “disruption of cleavage”. When a bundle of threading dislocations exists locally, a large stress concentration occurs in that portion. When the substrate is cleaved after the wafer process for manufacturing the laser element in a substrate shape, the cleavage plane is difficult to become a clean plane. It becomes a cleavage plane with vertical stripes perpendicular to the substrate surface. Since it is a single crystal, the cleavage plane should be a clean mirror surface. However, a GaN substrate that forcibly aggregates dislocations using facets tends to disturb the cleavage plane, and tends not to be a mirror surface.

  It is considered that the cleavage plane is disturbed by a random stress distribution caused by dislocation aggregation. If the cleavage plane is too disturbed even if LEDs and LDs are made using the bent GaN as a substrate, the cut end face must be further polished. It can no longer be said that it is superior to sapphire due to the increased number of processes. There is no armor using GaN with cleavage.

  In order to solve all of these problems, it is necessary to fundamentally reduce the threading dislocation density and eliminate the presence of dislocation bundles on the substrate surface. If there are no bundles of threading dislocations, there should be no disruption of the cleavage plane during cleavage.

  It is an object of the present invention to provide a GaN substrate manufacturing method and a GaN substrate that have a low threading dislocation density, do not have dislocation bundles on the substrate surface, and do not disturb the cleavage plane.

  In the present invention, a grown GaN single crystal ingot is sliced along a plane S parallel to the crystal growth direction g or the q direction in which dislocations extend, thereby producing a substrate. By cutting along the cutting plane S parallel to the crystal growth direction g or the dislocation extension direction q, threading dislocations on the substrate surface are reduced. If the substrate is cut in such a direction that the threading dislocations run parallel to the surface, the density of threading dislocations exposed on the surface decreases.

  In other words, the present invention reduces threading dislocations that have appeared on the surface by matching the threading dislocation direction with the surface. Even if there are many threading dislocations inside the substrate, the density of threading dislocations on the surface is low. Since internal dislocations do not affect device fabrication, if the number of threading dislocations on the surface is reduced, it can be suitably used as a device fabrication substrate.

  The purpose is to reduce surface threading dislocations, and the means is to cut a GaN single crystal ingot parallel to g or q to form a substrate. The present invention can be simply expressed by “g parallel S” or “q parallel S”. I promise to write here by the symbol “‖”. The present invention

q‖S (5)
g‖S (6)

Can be expressed by q and g are one-dimensional straight lines, and the surface S is two-dimensional. Therefore, even though S is parallel to q, S is not fixed. There is 180 degree of freedom of rotation around q. This is advantageous because the range of selection of the cut surface S is widened.

Depending on the crystal growth direction g, the extending direction q of threading dislocations may be stochastically distributed isotropically or may be determined uniformly. The threading dislocation extension direction q cannot be defined when it is stochastically varied. In that case, the present invention cannot be applied.
However, even if the extending direction q of threading dislocations is not uniformly determined, the threading dislocations do not vary isotropically. Thus, when q varies in the same plane, S that is q‖S exists. Therefore, the present invention can be applied in such a case.
Moreover, even if the extending direction q of threading dislocations is not determined uniformly, it can be limited to the orientation as long as it is oriented in a certain direction on the average in the variation. For this reason, S which becomes q‖S on average exists. Therefore, the present invention can be applied to such a case. However, the density of threading dislocations in that case largely depends on how the orientations are aligned in the variation.

  Further, if the threading dislocation extending direction q is uniformly determined, the threading dislocation extending direction q can be defined. Therefore, the cutting direction can be determined according to the equation (5). If so, the cutting direction S of “q‖S” can be adopted regardless of the growth direction. Does the threading dislocation extension direction q vary stochastically? Whether it is uniquely determined depends on the crystal growth direction g. With respect to the crystal orientation in which the threading dislocation direction q is uniquely determined, the cutting plane can be determined by q‖S by applying the present invention.

  FIG. 9 illustrates the conventional GaN ingot cutting. When a GaN single crystal ingot is grown upward (c-axis direction) as shown in FIG. 9A, threading dislocations also extend upward (c-axis direction). Conventionally, the ingot was cut parallel to the growth surface (C surface) as shown in FIG. Although a substrate (wafer) as shown in FIG. 9 (3) is obtained, the substrate surface is the C plane and the threading dislocation extending direction q is perpendicular to the plane. For this reason, as shown in FIG. 9 (4), a large dislocation density appeared on the surface of the GaN substrate.

  FIG. 10 illustrates the cutting of the present invention. As shown in FIG. 10A, threading dislocations extend in the crystal growth direction. The crystal growth surface and threading dislocations are orthogonal. In the present invention, the cut surface S is parallel to the threading dislocation. q‖S. Then, threading dislocations run parallel to the surface of the GaN substrate (wafer) as shown in FIG. As shown in FIG. 10 (3), the dislocation density on the surface decreases. Even if there is a lot of dislocation density inside, the surface density apparently decreases. Although the dislocation density does not actually decrease, the dislocation appearing on the surface decreases. It has already been mentioned that when making devices, the dislocation density on the surface is important and internal dislocations can be ignored. Moreover, the problem of unevenness of the cleavage plane in cleavage is also solved. FIG. 9 (4) and FIG. 10 (3) clearly show the difference between the conventional example and the present invention.

  Further, if the crystal growth direction g and the threading dislocation extension direction q match (g = q), the idea of the present invention can be expressed such that the growth direction g and the cut surface S are parallel. That is, g‖S, which is the above equation (6).

  In such a case, FIG. 10A can also be interpreted as cutting in parallel to the crystal growth direction g. The present invention also includes this case. Therefore, if q = g, q‖S and g‖S are the same.

  If it is the same, can I use only one expression? I think that is not the case. When a single crystal ingot is made, the growth direction g is known. However, the extension direction q of threading dislocations is not easily understood. It is necessary to cut out the substrate and etch it to produce dislocations and determine the direction. Therefore, it is practically more convenient to define the invention based on the growth direction g that can be readily understood.

  However, the present invention can of course be applied even when g ≠ q. In this case, priority is given to q‖S in the equation (5).

  Here, the word “reduction” of dislocation density will be explained just in case. Even if the cutting orientation is changed, the dislocation density that already exists is not reduced. This is because what already exists continues to exist regardless of the cutting plane orientation. Of course it is. It is said that the dislocation density exposed on the surface decreases. It can be said that surface dislocations are a problem in device fabrication, and intrinsic dislocations are irrelevant. Further, as shown in FIG. 10 (2), since the threading dislocation extending direction and the substrate surface are parallel, the natural cleavage plane is not disturbed. The problem of threading dislocation density is simple. E is the dislocation density in the plane perpendicular to the threading dislocations. This is the number of threading dislocations that cut the unit area. The number of threading dislocations that cut a plane inclined by φ relative to the plane is proportional to cos φ. Therefore, the dislocation density is Ecosφ. Since it is cut parallel to the threading dislocation extension direction, φ = 90 degrees. cos 90 ° = 0. That is, it is mathematically obvious that the dislocation density decreases in the cut surface of the present invention. In other words, it is natural.

  Fortunately, the present inventors have found that three of the GaN crystal planes have q = g. That is, it was found that there are three directions in which the crystal growth direction g is equal to the threading dislocation extension direction q. The three directions are referred to as c direction, m direction, and a direction. The planes perpendicular to them are defined as C plane, M plane, and A plane. that is

  M = {1-100}, A = {11-20}, C = {0001} (7)

It is. The corresponding directions are m = <1-100>, a = <11-20>, c = <0001>. When crystal growth is performed in these c, m, and a directions, since g = q, the cutting plane S can be determined in parallel to the crystal growth direction g.

  Even more conveniently, the three planes are orthogonal when taken in the proper combination. This is a very convenient property. That gives the present invention even greater versatility. Since they are hexagonal, the planes that are converted to each other by symmetry operations are equivalent. As mentioned above, there are six sides even if called M side. There are also six sides on the A side. There are two C-planes. All the A and C planes are orthogonal. All the M and C planes are orthogonal. An arbitrary A plane is orthogonal to the two M planes. An arbitrary M plane is orthogonal to the two A planes. Therefore, the “A” and “M” planes are orthogonal when “appropriate combinations are taken”. FIG. 11 shows such a combination. GaN is a hexagonal system, but has such an unexpected property that the three faces having a low plane index are orthogonal to each other. The present invention also takes advantage of this property.

  In addition to these three directions, there may be a growth direction in which g = q. The present invention can also be applied to such a growth direction. Of course. However, the fact that g = q on these three surfaces and they are orthogonal to each other gives an advantage difficult to obtain to the present invention.

  GaN does not grow easily in any direction. The three planes with the low plane index are planes that easily cause GaN crystal growth. That is, a GaN single crystal can be grown on the M, A, and C planes. Therefore, these three directions can be adopted as the growth direction g. That is, as a preferable crystal growth direction g

        g = m, a, c (8)

It can be. Such a combination is convenient due to the ease of growth.

  Conversely, the cut surface may be limited by the desired substrate orientation. It does not mean that a substrate with any orientation is acceptable. Since the substrate is a base for manufacturing a device, a C-plane substrate, an M-plane substrate, and an A-plane substrate having a low plane index are mainly required.

The cleaved surfaces of GaN are the C plane and the M plane. Therefore, when a device is made on an A-plane substrate, the two opposite sides become cleavage planes, and an LD resonator can be produced by natural cleavage. Even if a C-plane substrate is used, there is a cleavage plane on the opposite side, but there are cleavage planes in three directions, which may be inconvenient.

  In the M plane, the orthogonal C plane is a cleavage plane. In addition, a better surface state may be produced. Therefore, the preferred cut surface S is

S = M, A, C (9)
It is.

  FIG. 12 briefly shows the idea of the present invention that the substrate is cut parallel to the growth direction g. If the growth direction g is set to m, a, or c, and the cut surface S is set to any of M, A, or C orthogonal to it, the crystal grows in an easy growth direction, and a substrate having a high demand orientation can be manufactured. .

  The above is the basic form of the present invention. However, the true point of the present invention is to reduce dislocation by multi-stage growth. When GaN is grown on a substrate having dislocations parallel to the surface as shown in FIG. 10 (2) as a seed crystal, the number of dislocations is originally small, and the dislocation of the grown crystal inherits the dislocation of the seed crystal. There are fewer dislocations in the grown crystal. Therefore, according to the method of the present invention, when a second GaN growth is performed using a substrate cut at q = S or g = S as a seed crystal, it is possible to grow an ingot with a very low dislocation. . That is, dislocations can be reduced by changing the growth direction by 90 ° between the first and second growths. This decrease in dislocation is not an apparent decrease. The actual dislocations are reduced. Therefore, it can be said that the main feature of the present invention is fully demonstrated in the second and subsequent growths. In FIG. 12, a true low-dislocation crystal can be obtained by performing the second-stage crystal growth in the w-direction orthogonal to the first-stage growth direction g.

  This is a two-stage growth, but a three-stage growth or a four-stage growth is also possible. Each time, it is possible to repeat the process of making a substrate by cutting in parallel with the crystal growth direction, making an ingot with an orientation orthogonal to the seed crystal, and making a substrate by cutting further in parallel with the growth direction. Although the two planes are simply repeated, the three planes exist as orthogonal planes, so that a rich variety of combinations of growth directions can be brought about.

The background of the inventor's achievement of the present invention will be described below.
In GaN crystal growth, dislocations often extend in the crystal growth direction. For example, GaN epi-growth on a sapphire substrate, which is usually performed for manufacturing blue LEDs, is also true. It grows on the C-plane and has many dislocations extending mainly in the c-axis direction.

  In view of these facts, in order to reduce the threading dislocations, the present inventor would be effective in producing a substrate by cutting along a plane parallel to the crystal growth direction, that is, the direction in which the dislocations extend. I thought.

  The basic idea of the present invention is to create a situation in which dislocations exist in a specific plane and cut a plane parallel to the plane to produce a substrate with few threading dislocations on the substrate surface.

  This is a truly innovative idea. Who has ever conceived of cutting a crystal parallel to the crystal growth direction to cut out the substrate? An unparalleled crystal cutting direction.

  The present invention cuts the substrate in a direction parallel to the growth direction to reduce dislocations existing on the substrate surface. More specifically, the effect of reducing dislocations is obtained by changing the growth directions of the M, A, and C planes.

  That is, a GaN single crystal is grown in the {0001} plane direction and sliced parallel to the {1-100} plane or {11-20} plane, and the {1-100} plane or {11-20] having a low dislocation density. } Plane GaN single crystal substrate is manufactured (c; A, c; M). Alternatively, a GaN single crystal is grown in the {1-100} plane direction and sliced in parallel to the {0001} plane or the {11-20} plane to form a low dislocation density {0001} plane or {11-20} plane. A GaN single crystal substrate is manufactured (m; C, m; A). Alternatively, a GaN single crystal is grown in the {11-20} plane direction and sliced in parallel to the {0001} plane or {1-100} plane to obtain a low dislocation density {0001} plane or {1-100} plane. A GaN single crystal substrate is manufactured (a; C, a; M).

  Further, the single crystal thus formed is used as a seed crystal for further crystal growth. Two-stage or three-stage crystal growth may be performed. Since it grows from a low dislocation seed crystal, an ingot having a lower dislocation density can be obtained.

  According to the present invention, a wide GaN single crystal substrate having a low threading dislocation density can be manufactured. Since there is no accumulation of bundles of threading dislocations, the cleavage plane is not disturbed when cleaved. When the GaN substrate of the present invention is a GaInN-based LD substrate, a resonator can be formed by natural cleavage. When a GaInN-based LD or LED substrate is used, electrodes can be arranged above and below the chip. The area occupied by the electrodes can be saved. Further, when LD or LED is manufactured, it is not necessary to perform wire bonding twice like sapphire. In the case of using a GaInN-based LD or LED substrate, it is remarkably superior to the current sapphire substrate.

  The method of the present invention can be applied to GaN vapor phase synthesis methods such as HVPE, MOCVD, and sublimation. However, since it is the gist of the present invention that skillfully utilizes the property that threading dislocations extend parallel to the growth direction, the present invention can also be applied to GaN crystal growth methods other than vapor phase synthesis. This is a highly versatile technical idea that can be applied to the synthesis of GaN by the high pressure melting method.

  The basic concept of the present invention is to reduce the threading dislocations on the substrate surface by fabricating the substrate by slicing in a plane parallel to the crystal growth direction g or dislocation extending direction q in the growth of the GaN single crystal. ,That's what it means.

  First, the relationship between the direction of crystal growth and the direction in which dislocations extend, but the results of the inventors' research have revealed the following relationship.

  This is because a crystal sample having a plane orientation with the (0001) plane, (1-100) plane, and (11-20) plane as the surface is cut out from the ingot crystal, and these are used as seed crystals for further growth on the sample. The situation of crystal growth in a specific plane was grasped. Since GaN is a hexagonal system, it has four face indices and is difficult to understand intuitively, so these faces are named. The (0001) plane is called the C plane. The (1-100) plane is called the M plane. The (11-20) plane is referred to as the A plane. In this specification, these codes are sometimes used instead of the face index to make the relationship easy to understand.

  The crystal growth direction and the direction of dislocation were confirmed using a transmission electron microscope. As a result, in each of the samples of the (0001), (1-100), and (11-20) planes, mirror-like crystal growth was performed perpendicular to the crystal plane.

The relationship between the crystal growth and the average direction of dislocation extension was as follows.
(1) Crystal growth direction: <0001>, dislocation extension direction: <0001> (C-plane)
(2) Crystal growth direction: <1-100>, dislocation extension direction: <1-100> (M-plane)
(3) Crystal growth direction: <11-20>, dislocation extension direction: <11-20> (A surface)
In the case of C-plane, M-plane, and A-plane growth as in (1), (2), and (3) above, the direction in which dislocations extend in the crystal (referred to as dislocation extension direction q) is the crystal growth direction g. On average, it was almost the same direction.

  The present invention uses this property (g = q) to reduce threading dislocations in the substrate. However, in the (11-20) plane, there was a tendency that a facet plane was likely to appear depending on the growth conditions. However, the above result can be obtained by appropriately selecting the conditions.

  However, in the case of growth in other plane orientations, the direction of dislocations in the crystal (dislocation extension direction) is not necessarily the same as the crystal growth direction. The existence of the following was confirmed.

(4) Crystal growth direction: <1-101> R-plane direction, dislocation extension direction <1-100>
(5) Crystal growth direction: <11-22> F-plane direction, dislocation extension direction <11-20>

  In these cases (in the case of growth in the R-plane and F-plane directions), the crystal growth direction and the dislocation extension direction (g ≠ q) are different. The present invention does not say that these orientation growths are not utilized. On the other hand, when q ≠ g, q is prioritized and the ingot is cut by the cutting plane S parallel to the dislocation extension direction to form a substrate. The present invention can be applied to such a case where q ≠ g. In short, it is sufficient that the dislocation extension direction q can be uniquely defined. In these cases, multi-stage growth is possible, but if it is cut parallel to the dislocation extension direction, it is reduced to M-plane and A-plane crystals. Therefore, it will join somewhere in the following explanation. Therefore, these (4) and (5) examples will not be described later.

More practically speaking, the present invention cuts the ingot in the direction in which the dislocations run by utilizing the property that the dislocation extension direction q and the crystal growth direction g coincide with each other in the growth of the C, M, and A planes. Thus, a substrate with few threading dislocations is obtained.
For example, in the situation of the examples (1), (2), and (3) described above, an ingot is produced by growing a GaN crystal in the g direction (g = m, a, c), and the crystal growth direction g, that is, dislocation. An ingot is cut out in parallel (S surface) to the extending direction q of the wafer to form a wafer (S surface = A, M, C). As a result, a GaN substrate with reduced surface threading dislocations can be obtained. That is one stage of growth.

  In addition, the present invention can be applied to multi-stage growth and has a great effect in multi-stage growth. A thick GaN ingot is grown using a low dislocation substrate cut out parallel to the growth direction g as a seed crystal and cut parallel to the growth direction to obtain a low dislocation GaN substrate. If this process is repeated many times, dislocation inheritance can be prohibited and low dislocation can be achieved.

  The present invention is quite complicated, and many embodiments are difficult to understand intuitively. To help understanding, a simple notation is defined here. This makes it easy to understand the relationship between various embodiments of the present invention.

  In the case of a thin substrate, the surface orientation is expressed in alphabetic capital letters. The direction of crystal growth when a thick ingot is grown is expressed in lower case letters. In other words, it is expressed by substrate = upper case and ingot = lower case. For example, “Xx” means a process of growing a crystal thickly in the x direction on a seed crystal having an X plane, or an ingot having an X plane formed by the process as a growth plane.

  Since the orientation of the seed crystal and the epitaxial growth on it always match, the upper case letter and the lower case letter must match. Things like Xy, Yz ... are prohibited.

Slice processing is expressed by “;”. The direction of slicing is expressed by the capital letter following; For example, “Xx; Y” means that an ingot having an X-plane growth surface is formed on a seed crystal having an X-plane by growing it thick in the x-direction, and this is sliced in the Y-plane direction to have a Y-plane. The process of making a thin substrate (wafer), or a substrate made from it, is simply expressed.
This is a product operation.

  “Xx; Yy” means that an ingot having an X-plane growth surface is epitaxially grown on a seed crystal having an X-plane thickly in the x-direction, and this is sliced parallel to the Y-plane and thin with a Y-plane. It means a process of obtaining a substrate (wafer) and further epitaxially growing in the y direction using a Y-plane substrate as a seed crystal to obtain an ingot having a Y-plane growth surface, or an ingot having a Y-plane.

  “Xx; Yy; Z” means that an ingot having an X-plane growth surface is formed on a seed crystal having an X-plane by thickly growing it in the x-direction, and this is sliced parallel to the Y-plane to form the Y-plane. A thin substrate (wafer) is obtained, and an Y-plane substrate is used as a seed crystal for epi-growth in the y-direction to obtain an ingot whose growth surface is the Y-plane. It is assumed that a process of making a substrate (wafer) or a substrate made by the process is expressed.

  “Xx; Yy; Zz” means that an ingot having an X-plane growth surface is formed on a seed crystal having an X-plane to form an X-plane ingot, and this is sliced parallel to the Y-plane to form a Y-plane. A thin substrate (wafer) is obtained, and an Y-plane substrate is used as a seed crystal for epi-growth in the y-direction to obtain an ingot whose growth surface is the Y-plane. A substrate (wafer) having a Z-plane as a growth surface by making a substrate (wafer) having the substrate and epitaxial growth in the z direction as a seed crystal, or an ingot formed by the step is expressed. The same applies hereinafter.

Using this notation, a conventional GaN substrate manufacturing method for producing a plurality of C-plane substrates by epitaxially growing thickly in the c-direction on a C-plane seed crystal and slicing parallel to the C-plane is simply Cc; C It can be expressed as In slicing, as in c; C, the front and rear of; are the same, so there is no effect of reducing threading dislocations. If the conventional method = Cc; C is stored, the difference of the present invention will be readily understood.
In the slicing process, the present invention ultimately has different front and rear orientations, and the dislocation direction is the same as the cut surface direction after slicing, so that there is an effect of reducing threading dislocations. Therefore, since the crystal growth direction and the dislocation extension direction must match, the orientation is limited to the above-described C, M, and A. In short, the gist of the present invention is simply

              x; Y (x ≠ y) (10)

It is exhausted to the formula. This is a straightforward representation of the present invention. That is, the growth plane (X) is different from the cut plane (Y). This reduces the threading dislocation density. On the other hand, the conventional method is x; X.

  In the following, the story is limited to the mutual conversion of the three planes M, A, and C. Capital letters M, A, and C mean plane orientation, plane, and substrate. Small letters m, a, and c mean growth directions, ingots (crystals), or growth in that direction. In addition, the transformation of the growth direction is intuitively expressed by a figure.

  The growth direction is expressed by three downward arrows as shown in FIG. Let m = <1-100> be an arrow pointing downward to the left. Let a = <11-20> be the arrow pointing downward to the right. Let c = <0001> be a downward arrow. Arrows indicate growth progress. In the case of multi-stage growth, arrows indicating the growth direction continue downward. Such a crystal growth conversion is called a crystal growth diagram. 14 to 18 are main crystal growth diagrams of the present invention.

  When a substrate is formed by one-step growth and one slice processing, the present invention is limited to the following six (3 × 2) cases. This is shown in FIG.

(1) m; A (2) a; M
(3) a; C (4) m; C
(5) c; M (6) c; A (11)

  The dislocation reduction effect is expressed by the fact that the alphabet before and after is different. These six are basic forms. In other words, the following three are denied by the present invention: c; C, a; A, m; In particular, the conventional method is c; C.

  For example, (1) Mm; A means that an M plane epicrystal {1-100} plane is used for epitaxial growth in the m direction to form an ingot having the M plane as the growth surface, and the A plane ({11-20} In other words, the substrate is sliced parallel to the surface A) to produce a substrate having an A surface. Among these six cases, C and M, and C and A are particularly important for ease of production. In other words, the following four are promising from the viewpoint of ease of manufacture.

(6) c; A (5) c; M,
(4) m; C (3) a; C (12)

  These four may be referred to as CA type (6), CM type (5), MC type (4), and AC type (3) below. In addition to this, the MA type (1) and the AM (2) type are included in the formula (11) as one-step growth. These two are also interesting combinations, but since they are difficult to use in the actual growth process, they will not be described much later.

  Since there are six cases in one-stage growth, there are 6 × 2 = 12 different growth methods because two-stage growth allows two different orientations to follow. For example, the case of twelve-pure pure form 12 is given below. A diagram of this is shown in FIG.

(7) c; Aa; M (8) c; Aa; C (9) c; Mm; A
(10) c; Mm; C (11) m; Cc; A (12) m; Cc; M
(13) m; Aa; C (14) m; Aa; M (15) a; Cc; M
(16) a; Cc; A (17) a; Mm; C (18) a; Mm; A (13)

  However, since the combination of the seed crystal and the ingot crystal is always the same as Mm, Cc, and Aa, they are simply drawn as m, c, and a in the drawing. These are equally effective in reducing dislocations twice. However, when the crystal is actually grown, it is often grown in the c-axis direction.

(7) c; Aa; M (8) c; Aa; C
(9) c; Mm; A (10) c; Mm; C (14)

It is. Most importantly, a C-plane wafer is often required as the final wafer.

        (8) c; Aa; C (10) c; Mm; C (15)

These are two.

  In the case of three-stage growth, there are 6 × 2 × 2 = 24 different growth methods. This is shown in FIG.

(19) c; Aa; Mm; C (20) c; Aa; Cc; M (21) c; Mm; Aa; C
(22) c; Mm; Cc; M (23) m; Cc; Aa; M (24) m; Cc; Mm; A
(25) m; Aa; Cc; A (26) m; Aa; Mm; C (27) a; Cc; Mm; A
(28) a; Cc; Aa; C (29) a; Mm; Cc; A (30) a; Mm; Aa; C
(31) c; Aa; Mm; A (32) c; Aa; Cc; A (33) c; Mm; Aa;
(34) c; Mm; Cc; A (35) m; Cc; Aa; C (36) m; Cc; Mm; C
(37) m; Aa; Cc; M (38) m; Aa; Mm; A (39) a; Cc; Mm; C
(40) a; Cc; Aa; M (41) a; Mm; Cc; M (42) a; Mm; Aa;
(16)

These are the cases of a pure form that is always sliced in the dislocation direction during slicing. This has the effect of reducing threading dislocations in two stages and three stages.
But that is not all. It can also be said that once the dislocations are reduced, the dislocations need not be reduced in other stages. In that case, c; C, a; A, m; M are also allowed in any slicing process.

  If so, the present invention includes 3 × 3 × 3-3 = 24 in the case of two-stage growth and 3 × 3 × 3 × 3-3 = 78 types of manufacturing methods and substrates in the case of three-stage growth. Become. The 24 combinations in the case of the two-stage growth means that there are 12 sets in addition to 12 in the formula (13).

  If the first stage has a dislocation reduction effect and the second stage has no dislocation reduction effect (this is ultimately reduced in the case of one-stage growth), the following six are obtained. This is shown in FIG.

(43) c; Aa; A (44) c; Mm; M (45) m; Cc; C
(46) a; Cc; C (47) a; Mm; M (48) m; Aa; A
(17)

  If the first stage has no dislocation reduction effect and the second stage has a dislocation reduction effect, the following six cases can be obtained. This is shown in FIG.

(49) c; Cc; A (50) c; Cc; M (51) m; Mm; C
(52) a; Aa; C (53) a; Aa; M (54) m; Mm; A (18)

  Also in this case, since the initial growth direction is often the c-axis direction, four are important in that sense. Then, if we start from C-plane growth, together with equation (15)

(8) c; Aa; C (10) c; Mm; C
(43) c; Aa; A (44) c; Mm; M
(49) c; Cc; A (50) c; Cc; M (19)

Is important. The upper two have two dislocation reduction effects, and the lower four have one dislocation reduction effect.

  The claims themselves are quite complex. It is not easy to understand the relationship between each other. Therefore, it will be abbreviated as "contract ..." which corresponds to what is listed in the claims to make it easier to understand. The number attached to the diagram is attached to the back.

A (1) a; M (2) a; C (3) m; C (4) c; M (5) c; A (6) Contracts 1-4
5 = m; C (4)
6 = a; C (3)
7 = Mm; C (4)
8 × 7 = c; Mm; C (10) (58)
9 × 7 = m; Mm; C (51)

10 = Aa; C (3)
11 × 10 = c; Aa; C (8)
12 × 10 = a; Aa; C
13 = c; M (5) Contract 5
14 = Cc; M (5) Request 6
15 × 14 = Aa; Cc; M (15) Mm; Cc; M (12)
16 × 14 = Cc; Cc; M (50)
17 = c; A (6) Request 9

18 = Cc; A (6) Request 10
19 × 18 = Aa; Cc; A (16) Mm; Cc; A (11)
20 × 18 = Cc; Cc; A (49)
A (1) a; M (2) a; C (3) m; C (4) c; M (5) c; A (6)
27, 28 = m; C (4) Request 17, 18
29, 30 = a; C (3) Request 19, 20
31, 32 = c; M (5)
33, 34 = c; A (6) Request 23, 24
37 = c; Aa; A (43) a; Mm; M (47) m; Cc; C (45)
c; Mm; M (44) m; Aa; A (48) a; Cc; C (46)
38 = c; Aa; A (43) a; Mm; M (47) m; Cc; C (45)
c; Mm; M (44) m; Aa; A (48) a; Cc; C (46)
39 = m; Cc; C (45)
40 = a; Cc; C (46)
41 = c; Mm; M (44)

In the substrate proposed by the present invention, dislocations run parallel to the surface. Therefore, the number of threading dislocations exposed on the surface is reduced. This means six cases: c; M, m; A, a; C, c; A, a; M, m;
In addition, the direction in which dislocations run is mainly one direction, which reduces threading dislocations. This also means the same six groups: c; M, m; A, a; C, c; A, a; M, m;

  A more specific combination of orientations of the GaN substrate of the present invention will be described. Four types are possible depending on the growth direction and the direction of the cut surface.

I. MC type of {1-100} / {0001} (m; C and Mm; C)
A method of manufacturing a single crystal GaAs substrate having a (0001) plane in which a crystal growth plane is a {1-100} plane and is sliced by a (0001) plane parallel to the crystal growth direction.
The seed crystal has a {1-100} plane. The surface of the GaN substrate is a {0001} plane, and the threading dislocation direction is {1-100}.

B. AC type of {11-20} / {0001} (a; C and Aa; C)
A method for producing a single crystal GaAs substrate having a (0001) plane obtained by slicing a (0001) plane parallel to the crystal growth direction, wherein the crystal growth plane is a {11-20} plane.

The seed crystal has a {11-20} plane. The surface of the GaN substrate is a {0001} plane and the threading dislocation direction is {11-20}.
C. {0001} / {1-100} CM type (c; M and Cc; M)

  A method for producing a single-crystal GaAs substrate having a {1100} plane sliced by a {1-100} plane parallel to the crystal growth direction, the crystal growth plane being a {0001} plane.

  The seed crystal has a {0001} plane. The surface of the GaN substrate is a {1-100} plane and the threading dislocation direction is {0001}.

D. {0001} / {11-20} CA type (c; A and Cc; A)
A method of manufacturing a single crystal GaAs substrate having a {11-20} plane sliced by a {11-20} plane parallel to the crystal growth direction, the crystal growth plane being a {0001} plane.

  The seed crystal has a {0001} plane. The surface of the GaN substrate is a {11-20} plane, and the threading dislocation direction is {0001}.

Method for producing seed crystal of ({1-100} / {0001}) MC type (Mm)
A seed crystal (M) having a {1-100} plane necessary for crystal growth of a GaN crystal in the {1-100} plane direction (m) is produced as follows.
A. It can be manufactured by cutting out from a GaN crystal grown using the (0001) plane as a growth plane, with a {1-100} plane parallel to the growth direction. In the above notation, c; M.
A. It can be produced by cutting a {1-100} plane perpendicular to the growth direction from a GaN crystal grown using the {1-100} plane as a growth plane. In the above notation, m; M.
In the case of the seed crystal (1), formation of pits consisting of facet surfaces may be observed, but even if dislocation concentration occurs at the bottom of the pits, threading dislocations on the cut {1-100} plane are not high. No problem.
A crystal grown from a seed crystal having a low threading dislocation density has a low dislocation density. Further, when the cutout is cut out parallel to the growth direction (direction in which dislocations extend), it can be expected that the threading dislocation density is further reduced.

B. ({11-20} / {0001}) AC type seed crystal production method (Aa)
A seed crystal (A) having a {11-20} plane necessary for crystal growth of a GaN crystal in the {11-20} plane direction (a) is produced as follows.
1. It can be manufactured by cutting a {11-20} plane parallel to the growth direction from a GaN crystal grown with the (0001) plane as the growth plane (c; A).
2) It can be produced by cutting out from a GaN crystal grown using the {11-20} plane as a growth plane, along the {11-20} plane perpendicular to the growth direction (a; A).
In the case of the seed crystal (b), there may be formation of pits consisting of facet planes, but even if dislocation concentration occurs at the bottom of the pits, the threaded dislocations of the cut {11-20} plane are not high. No problem.
A crystal grown from a seed crystal having a low threading dislocation density has a low dislocation density. Further, when the cutout is cut out parallel to the growth direction (direction in which dislocations extend), it can be expected that the threading dislocation density is further reduced.

C ({0001} / {1-100}) CM type seed crystal production method (Cc)
A seed crystal (C) having a {0001} plane necessary for growing a GaN crystal in the {0001} plane direction (c) is manufactured as follows.
C. 1. It can be produced by cutting a {0001} plane parallel to the growth direction from a GaN crystal grown using the {11-20} plane as a growth plane (a; C).
2. It can be manufactured by cutting out from a {0001} plane parallel to the growth direction from a GaN crystal grown using the {1-100} plane as a growth plane (m; C).
C. It can be produced by cutting a {0001} plane perpendicular to the growth direction from a GaN crystal grown using the {0001} plane as a growth plane (c; C).
The manufacturing method itself (a; C, m; C) of C 1 and C 2 seed crystals is nothing but the implementation of the technical idea of the present invention, and the seed crystal itself is expected to have a considerably low threading dislocation density. The On top of that, a thick crystal ingot is epitaxially grown according to the idea of the present invention or not.
A crystal grown from a seed crystal having a low threading dislocation density has a low dislocation density. Further, when the cutout is cut out parallel to the growth direction (direction in which dislocations extend), it can be expected that the threading dislocation density is further reduced.

D. ({0001} / {11-20}) CA type seed crystal production method (Cc)
A seed crystal (C) having a {0001} plane necessary for growing a GaN crystal in the {0001} plane direction (c) is manufactured as follows.
1. It can be produced by cutting a {0001} plane parallel to the growth direction from a GaN crystal grown using the {11-20} plane as a growth plane (a; C).
D.2. It can be manufactured by cutting out from a {0001} plane parallel to the growth direction from a GaN crystal grown using the {1-100} plane as a growth plane (m; C).
D.3. It can be produced by cutting a {0001} plane perpendicular to the growth direction from a GaN crystal grown using the {0001} plane as a growth plane (c; C)).
The production method itself (a; C m; C) of the first and second seed crystals of D is nothing but the implementation of the technical idea of the present invention, and the seed crystal itself is expected to have a considerably low threading dislocation density. .
A crystal grown from a seed crystal having a low threading dislocation density has a low dislocation density. Further, when the cutout is cut out parallel to the growth direction (direction in which dislocations extend), it can be expected that the threading dislocation density is further reduced.

The GaN substrate thus obtained is a substrate having the following characteristics.
[I. MC type (m; C) (4)]
A single crystal GaN substrate in which the substrate surface is a {0001} plane and dislocations exist in the substrate mainly in the <1-100> direction, thereby reducing dislocations.
[B. AC type (a; C) (3)]
A single crystal GaN substrate whose substrate surface is a {0001} plane and dislocations exist mainly in the <11-20> direction in the substrate, thereby reducing dislocations.
[C. CM type (c; M) (5)]
A single crystal GaN substrate whose substrate surface is a {1-100} plane and dislocations exist mainly in the <0001> direction in the substrate, thereby reducing dislocations.
[D. CA type (c; A) (6)]
A single crystal GaN substrate whose substrate surface is a {11-20} plane and dislocations exist in the substrate mainly in the <0001> direction, thereby reducing dislocations.

The threading dislocations on the surface of the GaN substrate according to these inventions were measured. It was confirmed that the threading dislocation density was 1 × 10 ⁶ cm ⁻² or less.

  These inventions can also be applied when a GaN crystal is manufactured using a GaN crystal with reduced surface threading dislocations as a seed crystal.

  That is, the present invention can be applied to the case where the present invention is used to manufacture the seed crystal itself and a large single crystal is made from the seed crystal. He says he will grow in two stages. The dislocation reduction mechanism of the present invention is used twice. Therefore, threading dislocations can be reduced twice. In the above expression,

c; Aa; C c; Mm; C c; Aa; M c; Mm; A
m; Aa; C m; Aa; M m; Cc; A m; Cc; M
C; M a; Cc; A a; Mm; C a; Mm; A

There are 12 types of cases. Both of these have the same effect. In practice, however, the first growth is often performed in the c-axis direction using a foreign substance such as GaAs for the substrate. Then the really important of these 12

  c; Mm; C c; Mm; A c; Aa; C c; Aa; M

There are four types. In addition, a substrate having a C-plane is often required for the completed substrate itself. In that case, if it is further narrowed down and has a two-stage dislocation reduction mechanism,

c; Mm; C c; Aa; C
It is narrowed down to two types.

  However, it is also possible to apply the idea of the present invention only once in double growth. By slicing in a plane parallel to the crystal growth direction, a GaN single crystal with reduced threading dislocations penetrating the substrate surface on the slice processing surface is used as a seed crystal, or in the substrate mainly in one direction parallel to the substrate surface. A single-crystal GaN substrate in which dislocations run is used as a seed crystal, and a GaN substrate with low dislocations can be obtained by slicing in a plane perpendicular to the growth direction in the growth on the seed crystal. Although it is halfway from the idea of the present invention, a single low dislocation may be sufficient. In the above expression,

c; Aa; A c; Mm; M
m; Aa; A m; Cc; C
a; Cc; C a; Mm; M

There are six types.

  This is because a crystal having low dislocations according to the present invention is used as a seed crystal, and a crystal produced by growing on the seed crystal is sliced in a plane perpendicular to the growth direction to form a low dislocation substrate. Can be manufactured. In the final slicing process, threading dislocations run perpendicular to the surface, which is not necessarily preferable. However, since threading dislocations in the seed crystal are reduced, a relatively low dislocation GaN substrate can be obtained.

  Specifically, the crystal growth plane is {1-100}, and a single crystal sliced by a (0001) plane parallel to the crystal growth direction, or the crystal growth plane is a {11-20} plane, A single crystal sliced on a (0001) plane parallel to the direction is used as a seed crystal. By using these seed crystals having a (0001) plane to grow a crystal in the <0001> direction (with the {0001} plane as a growth plane), and slicing the {0001} plane perpendicular to the growth direction, A relatively low dislocation GaN crystal can be obtained.

  Further, the crystal growth plane is the (0001) plane, and a single crystal sliced by a {1-100} plane parallel to the crystal growth direction is used as a seed crystal, and a {1-100} plane is used as a growth plane thereon. A relatively low dislocation GaN crystal can be obtained by growing a GaN single crystal and slicing along a {1-100} plane perpendicular to the growth direction.

  The crystal growth method of the present invention can utilize a vapor phase growth method. For example, HVPE (Hydride Vapor Phase Epitaxy), MOCVD (Metalorganic Chemical Vapor Deposition), Organometallic Chloride Vapor Growth (Hydrogen Phase Vapor Growth) The present invention is based on the vapor phase growth method, but is not necessarily limited to the vapor phase growth method. The GaN crystal of the present invention can also be produced by applying an ultra-high pressure synthesis method that synthesizes at an ultra-high pressure.

  Among the vapor phase growth methods, some examples of the present invention will be described in the case of the HVPE method which is the simplest and is considered to have a high growth rate. The growth method may be an MOCVD method, a sublimation method, or an organic metal chloride vapor phase growth method. It can be applied to both.

In the HVPE method, in a hot-wall type furnace, Ga metal and HCl gas are reacted in the upstream portion to synthesize GaCl gas, and the reaction between NH ₃ gas and GaCl gas newly flowed in the vicinity of the substrate. Thus, GaN is grown on the substrate.

  There are five examples, but they are very similar, the difference is difficult to understand, and the relationship is complicated. Let us classify the examples according to the above notation in advance. FIGS. 19 to 23 show diagrams in the case of the first to fifth embodiments.

Example 1 (55) c; A (6) (56) c; M (5) (57) c; C
Example 2 (58) c; Mm; C (10) (59) c; Mm; M (68) c; Mm; A (69) c; Mm; Aa;
Example 3 (60) c; Aa; C (8) (61) c; Aa; A (70) c; Aa; M (71) c; Aa; Mm;
Example 4 (62) c; Mm; Cc; M (63) c; Mm; Cc; A
(64) c; Mm; Cc; C
Example 5 (65) c; Aa; Cc; A (66) c; Aa; Cc; M
(67) c; Aa; Cc; C

  In Example 1, seed crystals A, M, and C are prepared. In Example 2, an ingot m is grown from the seed crystal M of Example 1, and the substrates C and M are cut out. In Example 3, the ingot a is grown from the seed crystal A of Example 1, and the substrates C and A are cut out. In the fourth embodiment, an ingot c is made from the substrate C of the second embodiment, and the substrates C, M, and A are cut out. In the fifth embodiment, an ingot c is made from the substrate C of the third embodiment, and the substrates C, M, and A are cut out.

[Example 1: Preparation of seed crystal (c; A, c; M, c; C)]
First, GaN is grown in the c-axis direction from a GaAs substrate to produce a GaN seed crystal having an A plane, an M plane, and a C plane.

(I) Substrate
A GaAs substrate is used as a substrate to start crystal growth. When GaN is grown using a GaAs substrate, since GaN is a hexagonal system and GaAs is a cubic system, a substrate having a (111) plane of GaAs is used in order to achieve symmetry.

(B) SiO ₂ mask
A 0.1 μm thick SiO ₂ film was formed on the entire surface of the GaAs (111) substrate by plasma CVD as a mask. Thereafter, a window was opened in the mask by photolithography.

(C) Window formation
The mask window can have various shapes such as a stripe type and a dot type. Here, a dot-like window was formed. The dot-type window has a diameter of about 2 μm, and is arranged in a plurality of rows at a pitch of 4 μm in the <11-2> direction of the GaAs substrate, and is located 3.5 μm away from this dot row in the <1-10> direction Again, a plurality of dot windows were arranged in one row at a pitch of 4 μm in the <11-2> direction. However, the dot rows are shifted by 2 μm in the column direction in adjacent rows. In other words, the window arrangement has a two-dimensional expansion such that any three closest dot windows form a regular triangle having a side of 4 μm. The mask has such a window repeatedly (FIG. 2).

(D) HVPE equipment
Thereafter, GaN was grown on the GaAs substrate on which the mask was formed by the HVPE method (FIG. 1). A Ga metal boat is provided inside the atmospheric pressure reactor. Ga metal is in a molten state. A (111) GaAs substrate is placed on the sample below. All carrier gas and hydrogen gas H _2. Gases to be used are HCl gas (H ₂ + HCl) and NH ₃ gas (H ₂ + NH ₃ ).

HCl gas is allowed to flow through a Ga metal boat heated to 800 ° C. or higher. HCl gas and Ga react to synthesize GaCl gas. When this gas flows in the vicinity of the heated substrate, it reacts with the NH ₃ gas flowing in the vicinity of the substrate to become GaN, thereby forming a GaN layer on the GaAs substrate.

  This HVPE device is a device capable of long-term growth. This is because the growth rate of the GaN film is slow and it is necessary to grow a considerably thick GaN crystal.

(E) Formation of GaN buffer layer
An 80 nm GaN buffer layer was formed under the following conditions.
Growth temperature about 500 ° C (about 773K)
NH ₃ partial pressure of gas 0.2atm (20kPa)
HCl gas partial pressure 2 × 10 ⁻³ atm (0.2 kPa)
Growth time 30 minutes
Film thickness 80nm

  At this stage, a GaN buffer layer grows on the GaAs substrate surface of the mask window (the mask thickness is 100 nm and the buffer layer thickness is 80 nm). The buffer layer is grown at a low temperature and has an effect of adjusting the mismatch of lattice constants of GaAs and GaN.

(F) Formation of GaN epitaxial layer
Further, a GaN epilayer is grown thereon at a high temperature. The conditions are as follows.
Growth temperature 1020 ° C (1293K)
NH ₃ gas partial pressure 0.3atm (30kPa)
HCl gas partial pressure 2 × 10 ⁻² atm (2 kPa)
Growth time about 180 hours
Film thickness 3cm

Thus, a GaN ingot having a height of about 3 cm could be grown. The growth direction of the GaN ingot is the c-axis direction, and the growth surface is a C plane (0001) plane. Long ingots are expressed in lower case alphabets. Since this is a first generation ingot heteroepitaxially grown from GaAs with an ingot having a C plane, it can be expressed as “c ₁ ”.

  When the growth surface is observed with a microscope, growth pits comprising facets comprising reverse hexagonal pyramids and reverse dodecagonal pyramids composed of {11-22} planes, {1-102} planes, and the like are formed. It was found that there is a bundle of dislocations in the direction perpendicular to the growth plane.

  That is, it was confirmed that dislocations extend in the c-axis direction [0001], which is the growth direction, in the crystal.

(G) Preparation of seed crystal (c ₁ → M ₁ , A ₁ , C ₁ )
Since it has a thickness of 3 cm, seed crystals having various orientations can be cut out from this ingot having the (0001) growth surface. Here, seed crystals having the following three kinds of plane orientations were cut out.

(1) Seed crystal with principal surface {1-100} (M ₁ ) (56)
(2) (a _{A 1)} seed crystal and {11-20} plane major faces (55)
(3) Seed crystal with principal plane {0001} plane (referred to as C ₁ ) (57)

Since the GaN ingot has the (0001) plane as the surface, the conventional method of cutting in parallel with the surface only cuts the C ₁ substrate. However, the present invention covers such common sense and cuts out at right angles to the surface to produce substrates such as M ₁ and A ₁ . In the above notation, it corresponds to c; M and c; A.

Since these seed crystals are of the first generation produced by epitaxial growth based on a GaAs substrate, the suffix “1” is added. These seed crystals M ₁ , A ₁ , and C ₁ were evaluated.

(H) Evaluation of seed crystals
[Evaluation of Seed Crystal C ₁ (c; C)]
For the seed crystal C ₁ having a {0001} plane as the main surface, the presence of threading dislocations was evaluated by EPD (Etch Pit Density). However, the relationship between the original dislocation and the measured pit has not been fully clarified. Wet etching was performed to expose etch pits on the surface. The etchant is a mixed acid of phosphoric acid and sulfuric acid. When the seed crystal is etched at a temperature of 250 ° C., pits appear on the surface.

  When observed with a microscope, it was found that large pits were generated at the dislocation aggregate bundle. In other parts, the etch pit density was found to be considerably low.

  When the crystal was evaluated by cathodoluminescence (CL), it was found that the position where dislocation bundles existed and the position of pits appearing by this etching completely coincided with each other.

  As for the detected pits, pits having a diameter of about 10 μm to small pits having a diameter of about 1 μm were also observed.

  Thus, since there is a distribution in the presence of threading dislocations, it is difficult to express the threading dislocation density by one numerical value.

However, when these pits were counted ignoring the scale, the etch pits were ^calculated to be about 5 × 10 ⁵ cm ⁻² . Since the dislocation density of the conventional GaN crystal was 10 ⁷ cm ⁻² or more, it was confirmed that EPD was extremely reduced as compared with that.

[Evaluation of seed crystal M ₁ (c; M)]
EPD was measured by the same method for the seed crystal M ₁ having a {1-100} plane as the main surface. It was also found that pits were considerably reduced.
However, in the seed crystal M _1, it was confirmed that that there exists a pit row in the [0001] direction. The pit row is not a single row, but consists of a plurality of fairly dense rows. On the other hand, there was an area where no pits existed between the pit rows. Although the width of the area where no pits exist varies depending on the location, the average is about 200 μm.

[Evaluation of Seed Crystal A ₁ (c; A)]
EPD was measured by the same method for the seed crystal A ₁ having the {11-20} plane as the main surface. It was also found that pits were considerably reduced.
However, in the seed crystal A _1, it was confirmed that that there exists a pit array in the [0001] direction. The pit row is not a single row, but consists of a plurality of fairly dense rows. On the other hand, there was an area where no pits existed between the pit rows. The width of the area where pits do not exist was about 200 μm on average although it varied depending on the location.

Of these seed crystals C ₁ , A ₁ , M ₁ , A ₁ and M ₁ are used as seed crystals, and then a GaN ingot is produced. Then, a large number of substrates can be manufactured by cutting the ingot.

In Example 2, a GaN ingot is prepared using a seed crystal M ₁ and in Example 3 using a seed crystal A ₁ as a starting material.

If the seed crystal C ₁ as a starting material is not included in the category of the present invention. So for those of the seed crystal C ₁ and the raw material is not mentioned here. However, not all seed crystals C are denied. As will be described later, the seed crystal C once reduced in threading dislocation by the method of the present invention can be used as a starting material.

[Example 2; Production of GaN ingot m ₂ (using seed crystal M ₁ : c; Mm)]
A GaN ingot (m ₂ ) as described below was produced using the GaN seed crystal M ₁ having the {1-100} plane as the principal surface produced in Example 1. Since this ingot has two generations of GaN growth, it has a suffix of “2”. In the above notation, the growth is c; Mm.

Crystal growth was performed using the same HVPE furnace as the growth of the ingot for producing the seed crystal of Example 1. The carrier gas is all H ₂ gas. The gases used are NH ₃ gas (NH ₃ + H ₂ ) and HCl gas (H ₂ + HCl). Growth conditions are

Growth temperature 1020 ° C (1293K)
NH ₃ gas partial pressure 0.3atm (30kPa)
HCl gas partial pressure 2 × 10 ⁻² atm (2 kPa)
Growth time about 180 hours
Film thickness 2.5cm

Met. The growth direction is a <1-100> direction (referred to as m direction) perpendicular to the main surface {1-100} plane (M plane) of the seed crystal. Therefore, the final growth surface was {1-100} plane. The surface state was a mirror surface. The height of the ingot m ₂ was about 2.5 cm.

(A) Fabrication of C _m2 substrate (with C-plane) (c; Mm; C) (58)
By this the inner circumference slicer ingot _{m 2,} and cut out of the substrate is sliced in a direction parallel to the parallel and the (0001) plane in the growth direction <1-100>. In other words, it was sliced parallel to the threading dislocation.
According to the above notation, this is c; Mm; C. This will be written as C _{m @ 2} substrate by including a history from a second-generation substrate made from the seed crystal M _1. Thus, 25 GaN single crystal substrates having {0001} plane (C plane) on the surface could be cut out.

Those GaN substrates (C _m2 ) were 0.7 mm thick and 1 inch size substrates of about 25 mm × 30 mm. Thereafter, these substrates were polished. As a result, a substrate usable as a semiconductor substrate having no work-affected layer on the surface was obtained.

Evaluation was performed on the _Cm2 substrate. The (0001) Ga surfaces of the substrate _{C m @ 2} were evaluated by cathodoluminescence. Set of dislocations as seen in (0001) plane of the original GaN crystal c ₁ should excise the seed crystal M ₁ is found to be improved condition of the surface was not observed at all. The same substrate was evaluated by measuring EPD. Unlike the first seed crystal (C-plane), no large pits having a diameter of 10 μm to 20 μm were observed. All the pits were small pits having a diameter of 1 μm or less. Moreover, EPD was about 1 × 10 ⁴ cm ⁻² and a very low dislocation density.

The substrate C _m2 was observed with a TEM (transmission microscope). As a result, it was found that in these substrates _Cm2 , there are almost no threading dislocations on the (0001) plane. Although the number of dislocations is small, it was found that these dislocations mainly run in the <1-100> direction (m direction) parallel to the (0001) plane which is the substrate surface. The growth direction of the ingot is the m direction, and the extending direction of threading dislocations coincides with this. Since threading dislocations run parallel to the substrate surface, threading dislocations on the substrate surface are significantly reduced.

That is, it can be said that C _m2 is a substrate in which threading dislocations on the substrate surface are reduced by the presence of dislocations running parallel (m direction) to the (0001) plane (C plane) which is the substrate surface. The direction in which the dislocations run (m direction) is the growth direction of the GaN crystal (m direction), and the substrate C _m2 can be said to be a substrate sliced in a plane parallel to the growth direction of the crystal growth (m direction).

(B) Fabrication of M _m2 substrate (with M plane) (c; Mm; M) (59)
A GaN ingot m ₂ grown in the m direction using the seed crystal M ₁ was sliced on the {1-100} plane to produce a large number of the same substrates. From the beginning, this is c; Mm; M. Since the growth of GaN is repeated twice and the M substrate is used as a seed crystal, this can be written as M _m2 . It was confirmed that this M _m2 substrate had sufficiently low dislocations.

(C) Fabrication of A _m2 substrate (having A plane) (c; Mm; A) (68)
A GaN ingot m ₂ grown in the m direction using the seed crystal M ₁ was sliced on the {11-20} plane to produce a large number of the same substrates. From the beginning, this is c; Mm; A. Since the growth of GaN is repeated twice and the M substrate is used as a seed crystal, this can be written as _Am2 . It was confirmed that this _Am2 substrate had sufficiently low dislocations.

(D) Fabrication of C _a3 substrate (with C surface) (c; Mm; Aa; C) (69)
Was prepared by two growth substrates _{A m @ 2} of (c) as a seed crystal, to produce a plurality of GaN ingots _{a 3} by addition <11-20> direction growing a GaN single crystal into (a direction). Further, this was sliced on the (0001) plane to produce a number of (0001) GaN substrates _Ca3 having a C plane. This can be written because those made with There are three times the growth in the C board made based on the A substrate and the C _a3. If written from the beginning, this means c; Mm; Aa; C. This C _a3 substrate was confirmed to have sufficiently low dislocations.

[Example 3; Production of GaN ingot a ₂ (using seed crystal A ₁ : c; Aa)]
A GaN ingot (a ₂ ) as described below was produced using the GaN seed crystal A ₁ having the {11-20} plane as the principal surface produced in Example 1. Since this ingot has two generations of GaN growth, it has a suffix of “2”. In the above notation, the growth is c; Aa.
Crystal growth was performed using the same HVPE furnace as the growth of the ingot for producing the seed crystal of Example 1. The carrier gas is all H ₂ gas. The gases used are NH ₃ gas (NH ₃ + H ₂ ) and HCl gas (H ₂ + HCl). Growth conditions are

Growth temperature 1020 ° C (1293K)
NH ₃ gas partial pressure 0.3atm (30kPa)
HCl gas partial pressure 2 × 10 ⁻² atm (2 kPa)
Growth time about 180 hours
Film thickness 2.5cm

Met. The growth direction is a <11-20> direction (referred to as a direction) perpendicular to the main surface {11-20} plane (A plane) of the seed crystal. Therefore, the final growth surface was {11-20} plane. The surface state was a surface having a facet composed of {1-100} planes, although there was a mirror surface portion. The height of the ingot a ₂ was about 2.5 cm.

(A) Fabrication of C _a2 substrate (having C plane) (c; Aa; C) (60)
By The GaN ingots _{a 2,} cut out a substrate having a C plane is sliced in a direction parallel to the parallel and the (0001) plane in the growth direction <11-20> (a direction). In other words, it was sliced parallel to the threading dislocation.

According to the above notation, this means c; Aa; C. This will be written as C _a2 substrate moistened with history from a second-generation substrate made from the seed crystal A _1. Thus, 25 GaN single crystal substrates having {0001} plane (C plane) on the surface could be cut out.

Those GaN substrates (C _a2 ) were 0.7 mm thick and 1 inch size substrates of about 25 mm × 30 mm. Thereafter, these substrates were polished. As a result, a substrate C _a2 that has no work-affected layer on its surface and can be used as a semiconductor substrate was obtained.

Evaluation was performed on the _Ca2 substrate. The (0001) Ga surfaces of the substrate _{C a2} are estimated by the cathode luminescence. Set of dislocations as seen in (0001) plane of the original GaN crystal c ₁ to be cut out of the seed crystal A ₁ is was found that that improve the condition of the surface was not observed at all.

The same substrate was evaluated by measuring EPD. Unlike the original GaN crystal _{c 1} (0001) plane (C plane), large pits 10μm~20μm diameter was observed. All the pits were small pits having a diameter of 1 μm or less. Moreover, EPD was about 4 × 10 ⁴ cm ⁻² and a very low dislocation density.

This substrate C _a2 was observed with a TEM (transmission microscope). As a result, it was found that almost no threading dislocations exist on the (0001) plane in these substrates _Ca2 . Although the number of dislocations is small, it has been found that these dislocations mainly run in the <11-20> direction (a direction) parallel to the (0001) plane which is the substrate surface. The growth direction of the ingot is the a direction, and the extending direction of threading dislocations coincides with this. Since threading dislocations run parallel to the substrate surface, threading dislocations on the substrate surface are significantly reduced.

That is, it can be said that C _a2 is a substrate in which threading dislocations on the substrate surface are reduced by the presence of dislocations running parallel (a direction) to the (0001) plane (C plane) which is the substrate surface. The direction in which the dislocations run (direction a) is the growth direction of the GaN crystal (direction a), and this substrate can be said to be a (0001) substrate sliced in a plane parallel to the growth direction of crystal growth (direction a). .

(B) Production of A _a2 substrate (having A surface) (c; Aa; A) (61)
A GaN ingot a ₂ grown in the a direction using the seed crystal A ₁ was sliced on the {11-20} plane to produce a large number of the same substrates. From the beginning, this is c; Aa; A. Since the growth of GaN is repeated twice and the A substrate is used as a seed crystal, this can be written as _Aa2 . It was confirmed that this A _a2 substrate has sufficiently low dislocations.

(C) Fabrication of M _a2 substrate (with M plane) (c; Aa; M) (70)
A GaN ingot a ₂ grown in the a direction using the seed crystal A ₁ was sliced on the {1-100} plane to produce a large number of the same substrates. From the beginning, this is c; Aa; M.

Since the growth of GaN is repeated twice and the A substrate is used as a seed crystal, this can be written as _Ma2 . It was confirmed that this _{Ma 2} substrate had sufficiently low dislocations.

(D) Fabrication of C _m3 substrate (with C plane) (c; Aa; Mm; C) (71)
A plurality of GaN ingots m ₃ were produced by growing a GaN single crystal in the <1-100> direction (m direction) using the substrate _{Ma 2} produced by two growths as a seed crystal. Further, this was sliced on the (0001) plane to produce a number of (0001) GaN substrates _Cm3 having a C plane. This is a C substrate made based on the M substrate and made by three growths, so it can be written as C _m3 . When written from the beginning, this means c; Aa; Mm; C. This _Cm3 substrate was confirmed to have sufficiently low dislocations.

[Example 4: Production of GaN ingot c ₃ (using seed crystal C ₂ : c; Mm; Cc)]
A GaN ingot (c ₃ ) as shown below was produced by growing in the <0001> direction (c direction) using the GaN seed crystal C _m2 having the principal surface produced in Example 2 (a) as the (0001) plane. . This ingot has a suffix of “3” because it is the third generation of GaN growth. In the above-described notation, the growth is c; Mm; Cc.

Crystal growth was performed using the same HVPE furnace as the growth of the ingot for producing the seed crystal of Example 1. The carrier gas is all H ₂ gas. The gases used are NH ₃ gas (NH ₃ + H ₂ ) and HCl gas (H ₂ + HCl). Growth conditions are

Growth temperature 1020 ° C (1293K)
NH ₃ gas partial pressure 0.3atm (30kPa)
HCl gas partial pressure 2 × 10 ⁻² atm (2 kPa)
Growth time about 180 hours
Film thickness 3cm

Met. The growth direction is the <0001> direction (c direction) perpendicular to the main surface (0001) plane (C plane) of the seed crystal. The final growth surface was the (0001) plane. The surface state is a mirror surface with some growth pits. The height of the ingot _{c 3} was about 3cm.

(A) Preparation of C _c3 substrate (having C-plane) (c; Mm; Cc; C) (64)
By this the inner circumference slicer ingots c _3, were cut 30 sheets of substrates (C substrate) in the growth direction (0001) plane was sliced in a direction perpendicular. In other words, it was sliced in the direction across the threading dislocation.

According to the above notation, this means c; Mm; Cc; C. This moistened with history from the third generation of substrate made from the seed crystal C ₂ to be written as C _c3 substrate. In this manner, 30 GaN (C _c3 ) single crystal substrates having {0001} plane (C plane) on the surface could be cut out.

_These GaN substrates (C _c3 ) were 0.7 mm thick and 1 inch size substrates of about 30 mm × 30 mm. Thereafter, these substrates were polished. As a result, a substrate usable as a semiconductor substrate having no work-affected layer on the surface was obtained.

Evaluation was performed on the _Cc3 substrate. The (0001) Ga surfaces of the substrate _{C c3} was evaluated by cathodoluminescence. Set of dislocations as seen in (0001) plane of the original GaN crystal c ₁ should excise the seed crystal M ₁ is found to be improved condition of the surface was not observed at all.

The same substrate was evaluated by measuring EPD. Unlike the (0001) plane (C plane) of the initial GaN crystal c _{1 from which} the _first seed crystal M ₁ should be cut, no large pits having a diameter of 10 μm to 20 μm were observed. All the pits were small pits having a diameter of 1 μm or less. Moreover, EPD was about 1 × 10 ⁴ cm ⁻² and a very low dislocation density.

The substrate _Cc3 was observed with a TEM (transmission microscope). As a result, it was found that in these substrates _Cc3 , there are almost no threading dislocations on the (0001) plane. Although the number of dislocations is small, these dislocations also run almost through in the <1-100> direction (m direction) and <11-20> direction (a direction), which are parallel to the (0001) plane which is the substrate surface. It turns out that not.

The reason for the low dislocation is considered as follows. A low dislocation C-plane substrate C _m2 (c; Mm; C) having threading dislocations running on the substrate surface is grown as a seed crystal in the c direction <0001> direction, and the low threading dislocation state is transferred in the <0001> direction. This is because the substrate C _c3 (c; Mm; Cc; C) sliced on the C plane from the structure ingot c ₃ (c; Mm; Cc). Therefore, the substrate _Cc3 has a low threading dislocation density on the surface and few dislocations running parallel to the surface. It is an ideal substrate.

(B) Fabrication of M _c3 substrate (with M plane) (c; Mm; Cc; M) (62)
By this the inner circumference slicer ingots _{c 3,} were cut 30 substrates M with in parallel to sliced parallel {1-100} plane in the growth direction <0001> {1-100} plane. In other words, it was sliced parallel to the threading dislocation. This is the way of thinking of the present invention.

According to the above notation, this is c; Mm; Cc; M. This moistened with history from the third generation of substrate made from the seed crystal C ₂ to be written as M _c3 substrate. Thus, 30 GaN single crystal substrates having {1-100} plane (M plane) on the surface could be cut out.

_These GaN substrates (M _c3 ) were 0.7 mm thick and 1 inch size substrates of about 30 mm × 25 mm. Thereafter, these substrates were polished. As a result, a substrate _Mc3 that can be used as a semiconductor substrate and has no work-affected layer on the surface was obtained.

Evaluation was performed on the _Mc3 substrate. The substrate surface {1-100} plane of the substrate _{M c3} was evaluated by cathodoluminescence (CL). Set of dislocations as seen in (0001) plane of the original GaN crystal c ₁ should excise the seed crystal M ₁ is found to be improved condition of the surface was not observed at all.

The {1-100} plane of the same substrate _Mc3 was evaluated by measuring EPD. Unlike the (0001) plane (C plane) of the initial GaN crystal c _{1 from which} the _first seed crystal M ₁ should be cut, no large pits having a diameter of 10 μm to 20 μm were observed. All the pits were small pits having a diameter of 1 μm or less. Moreover, EPD was about 8 × 10 ³ cm ⁻² and a very low dislocation density.

The {1-100} plane of the substrate _Mc3 was observed with a TEM (transmission microscope). As a result, it was found that in these substrates _Mc3 , almost no threading dislocations exist on the {1-100} plane. It was found that the number of dislocations was small and few dislocations ran parallel to the substrate surface {1-100}. For this reason, the low density of the surface is greatly reduced.

The reason for the low dislocation is considered as follows. A low dislocation C-plane substrate C _m2 (c; Mm; C) having threading dislocations running on the substrate surface is grown as a seed crystal in the c direction <0001> direction, and the low threading dislocation state is transferred in the <0001> direction. This is because the substrate M _c3 (c; Mm; Cc; M) sliced on the M plane parallel to the growth direction from the structure ingot c ₃ (c; Mm; Cc). Therefore, the substrate _Mc3 has a low surface threading dislocation density and few dislocations running parallel to the surface. It is an ideal substrate.

(C) Preparation of an A _c3 substrate (having an A surface) (c; Mm; Cc; A) (63)
By this the inner circumference slicer ingots _{c 3,} were cut 30 substrates A, in parallel to slicing the {11-20} plane parallel to the growth direction <0001> with {11-20} plane. In other words, it was sliced parallel to the threading dislocation. This is the way of thinking of the present invention.

According to the above notation, this means c; Mm; Cc; A. This moistened with history from the third generation of substrate made from the seed crystal C ₂ to be written as A _c3 substrate. In this way, 30 GaN single crystal substrates having {11-20} plane (A plane) on the surface could be cut out.
Those GaN substrates (A _c3 ) were 0.7 mm thick and 1 inch size substrates of about 30 mm × 25 mm. Thereafter, these substrates were polished. As a result, a substrate _Ac3 usable as a semiconductor substrate having no work-affected layer on the surface was obtained.

Evaluation was performed on the _Ac3 substrate. The substrate surface {11-20} plane of the substrate _{A c3} was evaluated by cathodoluminescence (CL). Set of dislocations as seen in (0001) plane of the original GaN crystal c ₁ should excise the seed crystal M ₁ is found to be improved condition of the surface was not observed at all.

The {11-20} plane of the same substrate _Ac3 was evaluated by measuring EPD. Unlike the (0001) plane (C plane) of the initial GaN crystal c _{1 from which} the _first seed crystal M ₁ should be cut, no large pits having a diameter of 10 μm to 20 μm were observed. All the pits were small pits having a diameter of 1 μm or less. Moreover, EPD was about 1 × 10 ⁴ cm ⁻² and a very low dislocation density.

The {11-20} plane of this substrate _Ac3 was observed with a TEM (transmission microscope). As a result, it was found that in these substrates _Ac3 , there are almost no threading dislocations on the {11-20} plane. It was found that the number of dislocations was small and few dislocations ran parallel to the substrate surface {11-20}. For this reason, the low density of the surface is greatly reduced.

The reason for the low dislocation is considered as follows. A low dislocation C-plane substrate C _m2 (c; Mm; C) having threading dislocations running on the substrate surface is grown as a seed crystal in the c direction <0001> direction, and the low threading dislocation state is transferred in the <0001> direction. This is because the substrate A _c3 (c; Mm; Cc; A) sliced on the A plane parallel to the growth direction from the ingot c ₃ (c; Mm; Cc) of the structure. Therefore, the substrate _Ac3 has a low threading dislocation density on the surface and few dislocations running parallel to the surface. It is an ideal substrate.

Example 5: Preparation of GaN ingots _{c 3} (with a seed crystal _{C 2: c; Aa; Cc} )]
A GaN ingot (c ₃ ) as described below was fabricated by growing in the <0001> direction (c direction) using the GaN seed crystal C _a2 having the (0001) plane as the principal surface produced in Example 3. This ingot has a suffix of “3” because it is the third generation of GaN growth. In the above-mentioned notation, the growth is c; Aa; Cc.

Crystal growth was performed using the same HVPE furnace as the growth of the ingot for producing the seed crystal of Example 1. The carrier gas is all H ₂ gas. The gases used are NH ₃ gas (NH ₃ + H ₂ ) and HCl gas (H ₂ + HCl). Growth conditions are

Growth temperature 1020 ° C (1293K)
NH ₃ gas partial pressure 0.3atm (30kPa)
HCl gas partial pressure 2 × 10 ⁻² atm (2 kPa)
Growth time about 180 hours
Film thickness 2.7cm

Met. The growth direction is the <0001> direction (c direction) perpendicular to the main surface (0001) plane (C plane) of the seed crystal. The final growth surface was the (0001) plane. The surface state is a mirror surface with some growth pits. The height of the ingot _{c 3} is about 2.7 cm. A plurality of such ingots were grown.

(A) Preparation of C _c3 substrate (having C-plane) (c; Aa; Cc; C) (67)
By this the inner circumference slicer ingots c _3, were cut 30 sheets of substrates (C substrate) in the growth direction (0001) plane was sliced in a direction perpendicular. In other words, it was sliced in the direction across the threading dislocation.
According to the above notation, this means c; Aa; Cc; C. This moistened with history from the third generation of substrate made from the seed crystal C ₂ to be written as C _c3 substrate. In this manner, 30 GaN (C _c3 ) single crystal substrates having {0001} plane (C plane) on the surface could be cut out.

_These GaN substrates (C _c3 ) were 0.7 mm thick and 1 inch size substrates of about 30 mm × 25 mm. Thereafter, these substrates were polished. As a result, a substrate usable as a semiconductor substrate having no work-affected layer on the surface was obtained.

Evaluation was performed on the _Cc3 substrate. The substrate surface (0001) Ga surface of the substrate _Cc3 was evaluated by cathodoluminescence (CL). Set of dislocations as seen in (0001) plane of the original GaN crystal c ₁ to be cut out of the seed crystal A ₁ is was found that that improve the condition of the surface was not observed at all.

The same substrate was evaluated by measuring EPD. Unlike the (0001) plane (C plane) of the original GaN crystal c _{1 from which} the _first seed crystal A ₁ should be cut, no large pits having a diameter of 10 μm to 20 μm were observed. All the pits were small pits having a diameter of 1 μm or less. It was found that the pits tend to line up in the <11-20> direction. Moreover, EPD was about 5 × 10 ⁴ cm ⁻² and a low dislocation density.

The substrate _Cc3 was observed with a TEM (transmission microscope). As a result, it was found that in these substrates _Cc3 , there are almost no threading dislocations on the (0001) plane. It was found that the number of dislocations is small, and not only that, there are few threading dislocations running on the substrate surface. For this reason, the dislocation density in the substrate plane is greatly reduced.

The reason for the low dislocation is considered as follows. A low dislocation C-plane substrate C _a2 (c; Aa; C) with threading dislocations running on the substrate surface is grown as a seed crystal in the c direction <0001> direction, and the low threading dislocation state is transferred in the <0001> direction. This is because the substrate C _c3 (c; Aa; Cc; C) sliced on the C plane from the structure ingot c ₃ (c; Aa; Cc). Therefore, the substrate _Cc3 has a low threading dislocation density on the surface and few dislocations running parallel to the surface. It is an ideal substrate.

(B) Fabrication of M _c3 substrate (with M plane) (c; Aa; Cc; M) (66)
By The GaN ingots _{c 3,} the 30 substrates M that in parallel to sliced parallel {1-100} plane in the growth direction [0001] (M plane) having {1-100} plane I cut it out. In other words, it was sliced parallel to the threading dislocation. This is the way of thinking of the present invention.

According to the above notation, this means c; Aa; Cc; M. This moistened with history from the third generation of substrate made from the seed crystal C ₂ to be written as M _c3 substrate. Thus, 30 GaN single crystal substrates having {1-100} plane (M plane) on the surface could be cut out.

_These GaN substrates (M _c3 ) were 0.7 mm thick and 1 inch size substrates of about 30 mm × 25 mm. Thereafter, these substrates were polished. As a result, a substrate _Mc3 that can be used as a semiconductor substrate and has no work-affected layer on the surface was obtained.

Evaluation was performed on the _Mc3 substrate. The surface of the substrate _{M c3} {1-100} are estimated by the cathode luminescence (CL). Set of dislocations as seen in (0001) plane of the original GaN crystal c ₁ to be cut out of the seed crystal A ₁ is was found that that improve the condition of the surface was not observed at all.

The {1-100} plane of the same substrate _Mc3 was evaluated by measuring EPD. Unlike the (0001) plane (C plane) of the original GaN crystal c _{1 from which} the _first seed crystal A ₁ should be cut, no large pits having a diameter of 10 μm to 20 μm were observed. All the pits were small pits having a diameter of 1 μm or less. Moreover, EPD was about 1 × 10 ⁴ cm ⁻² and a low dislocation density.

The {1-100} plane of the substrate _Mc3 was observed with a TEM (transmission microscope). As a result, it was found that in these substrates _Mc3 , almost no threading dislocations exist on the {1-100} plane. It was found that the number of dislocations was small and a small number of dislocations ran parallel to the substrate surface {1-100} plane. For this reason, the low density of the surface is greatly reduced.

The reason for the low dislocation is considered as follows. A low dislocation C-plane substrate C _a2 (c; Aa; C) with threading dislocations running on the substrate surface is grown as a seed crystal in the c direction <0001> direction, and the low threading dislocation state is transferred in the <0001> direction. This is because the substrate M _c3 (c; Aa; Cc; M) sliced on the M plane parallel to the growth direction from the structure ingot c ₃ (c; Aa; Cc). Therefore, the substrate _Mc3 has a low surface threading dislocation density and few dislocations running parallel to the surface. It is an ideal substrate.

(C) Fabrication of _Ac3 substrate (having A surface) (c; Aa; Cc; A) (65)
By this the inner circumference slicer ingots _{c 3,} were cut 30 substrates A, in parallel to slicing the {11-20} plane parallel to the growth direction <0001> with {11-20} plane. In other words, it was sliced parallel to the threading dislocation. This is the way of thinking of the present invention.

According to the above notation, this means c; Aa; Cc; A. This moistened with history from the third generation of substrate made from the seed crystal C ₂ to be written as A _c3 substrate. In this way, 30 GaN single crystal substrates having {11-20} plane (A plane) on the surface could be cut out.
Those GaN substrates (A _c3 ) were 0.7 mm thick and 1 inch size substrates of about 30 mm × 25 mm. Thereafter, these substrates were polished. As a result, a substrate _Ac3 usable as a semiconductor substrate having no work-affected layer on the surface was obtained.

Evaluation was performed on the _Ac3 substrate. The substrate surface {11-20} plane of the substrate _{A c3} was evaluated by cathodoluminescence (CL). Set of dislocations as seen in (0001) plane of the original GaN crystal c ₁ to be cut out of the seed crystal A ₁ is was found that that improve the condition of the surface was not observed at all.

The {11-20} plane of the same substrate _Ac3 was evaluated by measuring EPD. Unlike the (0001) plane (C plane) of the original GaN crystal c _{1 from which} the _first seed crystal A ₁ should be cut, no large pits having a diameter of 10 μm to 20 μm were observed. All the pits were small pits having a diameter of 1 μm or less. Moreover, EPD was about 2 × 10 ⁴ cm ⁻² and a very low dislocation density.

The {11-20} plane of this substrate _Ac3 was observed with a TEM (transmission microscope). As a result, it was found that in these substrates _Ac3 , there are almost no threading dislocations on the {11-20} plane. It was found that the number of dislocations was small and few dislocations ran parallel to the substrate surface {11-20}. For this reason, the low density of the surface is greatly reduced.

The reason for the low dislocation is considered as follows. A low dislocation C-plane substrate C _a2 (c; Aa; C) with threading dislocations running on the substrate surface is grown as a seed crystal in the c direction <0001> direction, and the low threading dislocation state is transferred in the <0001> direction. This is because the substrate A _c3 (c; Aa; Cc; A) sliced on the A plane parallel to the growth direction from the ingot c ₃ (c; Aa; Cc) of the structure. Therefore, the substrate _Ac3 has a low threading dislocation density on the surface and few dislocations running parallel to the surface. It is an ideal substrate.

The schematic sectional drawing of an HVPE apparatus.

The top view of the state which formed the mask on the GaAs substrate and made the square window open for lateral overgrowth growth of GaN.

The top view of the state which formed the mask on the GaAs substrate and made the stripe window open for lateral overgrowth growth of GaN.

Sectional drawing which shows a mode that GaN accumulates on a GaAs substrate in lateral overgrowth growth. Fig. 4 (1) shows a state in which a GaAs substrate is covered with a mask and a window is opened. FIG. 4 (2) shows a state in which GaN is deposited on the window. FIG. 4 (3) shows a state in which GaN grows laterally from the window. FIG. 4 (4) shows a state in which the laterally grown layers are combined and converted into upward growth.

Sectional drawing which shows a mode that GaN accumulates on a GaAs substrate in lateral overgrowth growth. Fig. 5 (1) shows a state in which a GaAs substrate is covered with a mask and a window is opened. FIG. 5 (2) shows a state where a thick epi layer grows far beyond the window and becomes a thick GaN ingot. FIG. 5 (3) shows a state where the ingot is cut perpendicularly to the growth direction to form a substrate.

FIG. 6 is a diagram for explaining that the plane orientations h, k, and m are defined by the distances that cut three axes a, b, and d that form an angle of 120 ° on the C plane in a hexagonal crystal system.

The figure for demonstrating that the sum of three surface orientation h, k, m on the same plane of a hexagonal system is 0.

The figure which shows the (1-100) plane and the (11-20) plane in a hexagonal crystal system.

The figure explaining the conventional growth and cutting | disconnection method which makes it grow in a c-axis direction and cut | disconnects parallel to a C surface, and makes it a board | substrate.

The figure explaining the growth and cutting | disconnection method of this invention made into a board | substrate by making it grow in arbitrary directions and cut | disconnect at a cut surface parallel to a growth direction.

If an appropriate plane is selected, it will be explained that the A plane = {11-20} plane, the M plane = {1-100} plane, and the C plane = {0001} plane are orthogonal to each other. The perspective view of the crystal plane for demonstrating what is implement | achieved by the conversion of the mutual growth direction of a surface and M surface.

The perspective view of the crystal plane for showing the method of this invention which reduces the density in the surface of a threading dislocation by cutting out a board | substrate by making the crystal growth direction g and the cut surface S in parallel.

Definition diagram illustrating that the arrows correspond to the a, c, and m directions so that the present invention can be visually distinguished from the mutual conversion of the growth directions of the A, C, and M planes. .

In the present invention in which the dislocation density is reduced by making the growth direction and the direction of the cut surface parallel, there are six possible combinations of the crystal growth direction and the substrate surface in one-step growth, which are represented by the arrows defined above. A diagram expressed by.

In the present invention in which the dislocation density is reduced by making the growth direction and the direction of the cut surface parallel, there are 12 possible combinations of the crystal growth direction and the substrate surface in which the growth direction is different in the two-stage growth. Is a diagram expressed by the arrow defined above.

In the present invention in which the dislocation density is reduced by making the growth direction and the direction of the cut surface parallel, there are 24 possible combinations of crystal growth direction and substrate surface in which the growth direction is different in all three-stage growth, Is a diagram expressed by the arrow defined above.

In the two-stage growth, the first stage has different growth directions, and the two stages have six possible combinations of crystal growth direction and substrate surface, assuming that the growth directions are the same, and this is expressed by the arrows defined above.

In the two-stage growth, there is six possible combinations of crystal growth directions and substrate planes in which the first stage has the same growth direction and the two stages have different growth directions, and this is represented by the arrows defined above.

2 is a diagram showing a change in orientation in crystal growth and substrate cutting in Example 1. FIG.

6 is a diagram showing a change in orientation in crystal growth and substrate cutting in Example 2. FIG.

6 is a diagram showing a change in orientation in crystal growth and substrate cutting in Example 3. FIG.

6 is a diagram showing a change in orientation in crystal growth and substrate cutting in Example 4. FIG.

6 is a diagram showing a change in orientation in crystal growth and substrate cutting in Example 5. FIG.

Explanation of symbols

1 furnace
2Ga boat
3Ga melt
4 susceptors
5GaAs substrate
6 heaters
7 gas inlet
8 gas inlet
9 gas outlet
10GaAs wafer
11 masks
12 windows
13 ridges
14 rearrangement
15 horizontal extension layers
16 facets
17 surface defects
18GaN epi layer (ingot)
19GaN substrate (mirror wafer)
S cut surface
g Crystal growth direction
q Dislocation extension direction

Claims (1)

A GaN single crystal grown by any one of the HVPE method, the MOCVD method, and the organometallic chloride vapor phase growth method, and grown using the {11-20} plane or the {1-100} plane as the growth plane By growing a GaN single crystal having a {0001} plane cut out from the crystal as a {0001} plane as a seed crystal and a {0001} plane as a growth plane, and slicing the {1-100} plane, A method for producing a single crystal GaN substrate, comprising a {1-100} plane on the surface .

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