JP2009023853A - Group iii-v nitride semiconductor substrate, method for manufacturing the same, and group iii-v nitride semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a group III-V nitride semiconductor substrate and a method for manufacturing the substrate in which fluctuation in plane orientation of the substrate surface can be decreased by reducing warpage of the substrate in an as-grown state, and to provide a group III-V nitride semiconductor device using the above substrate and having excellent uniformity in the substrate plane. <P>SOLUTION: A light emitting element is fabricated by using a GaN self-standing substrate 10 and by forming an epitaxial layer comprising a GaN semiconductor crystal on the substrate, the substrate having a dislocation density of not more than 3×10<SP>6</SP>cm<SP>-2</SP>on the back face of the substrate and showing decrease in the dislocation density by a rate of not more than 3×10<SP>6</SP>cm<SP>-2</SP>/mm in the thickness direction from the back face to the top face of the substrate. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a group III-V nitride semiconductor substrate, a method for manufacturing the same, and a group III-V nitride semiconductor device, and more particularly, by reducing the warpage of the substrate in an as grown state. III-V nitride semiconductor substrate capable of reducing variations in surface plane orientation and method for manufacturing the same, and short-wavelength LD (laser diode) excellent in in-plane uniformity using the substrate, The present invention relates to a group III-V nitride semiconductor device such as an LED (light emitting diode) and a high breakdown voltage HEMT (high electron mobility transistor).

  Nitride semiconductor materials have a sufficiently large forbidden band and a direct transition type between bands, and are therefore used in the manufacture of short wavelength light emitting devices, particularly blue light emitting diodes (LEDs). In addition, recently, ultraviolet LEDs with shorter wavelengths and white LEDs in which these LEDs and phosphors are combined have begun to be put into practical use.

  When a semiconductor device is manufactured, so-called homoepitaxial growth is generally performed using a substrate having the same lattice constant and linear expansion coefficient as that of a crystal to be epitaxially grown as an underlying substrate. For example, a GaAs single crystal substrate is used as a substrate for epitaxial growth of GaAs or AlGaAs.

  However, it has not been possible to produce a group III-V nitride semiconductor substrate having a size and characteristics sufficient for practical use so far only for a group III-V nitride semiconductor crystal. For this reason, most nitride-based light-emitting diodes that have been put to practical use so far are formed on a sapphire substrate having a lattice constant close to that of a group III-V nitride-based semiconductor using a metal organic vapor phase epitaxy (MOVPE) method. Manufactured by heteroepitaxial growth of crystals. Therefore, various problems due to hetero-growth have occurred.

  For example, due to the difference in coefficient of linear expansion between the sapphire substrate and GaN, there has been a problem that the substrate after epitaxial growth is greatly warped. This causes a decrease in yield, such as cracking of the substrate in the photolithography process and chip processing process after epitaxial growth.

Also, since the lattice constants of sapphire substrate and GaN are different, in order to grow a single crystal of nitride crystal, it is necessary to deposit a buffer layer at a temperature lower than the original crystal growth temperature, which is the process of crystal growth It is a factor that extends time. Further, in the growth on the sapphire substrate, as many as 10 ⁸ to 10 ⁹ dislocations / cm ⁻² are generated in the GaN epilayer due to the difference in lattice constant between sapphire and GaN. This dislocation is a factor that hinders the output and reliability of the light emitting element. In conventional blue LEDs, dislocation has not been a problem so far, but higher output will be required in the future, and shortening of the wavelength will be promoted toward the realization of ultraviolet LEDs. Then, it is expected that the effect of dislocations on device characteristics will increase, and some countermeasures are required.

  In order to solve these problems, GaN single crystal free-standing substrates have been developed in recent years. As a method for manufacturing a GaN free-standing substrate, for example, a so-called ELO (Epitaxial Lateral Overgrowth) technique is used, in which a mask having an opening is formed on a base substrate and a GaN layer with few dislocations is obtained by lateral growth from the opening. It has been proposed to form a GaN layer on a sapphire substrate and then remove the sapphire substrate by etching or the like to obtain a GaN free-standing substrate (see, for example, Patent Document 1).

  Further, as a further development of the ELO method, a FIELO (Facet-Initiated Epitaxial Lateral Overgrowth) method has been developed (for example, see Non-Patent Document 1). The FIELO method is common to the ELO method in that selective growth is performed using a silicon oxide mask, but differs in that facets are formed in the mask opening during selective growth. By forming facets, the propagation direction of dislocations is changed, and threading dislocations reaching the upper surface of the epitaxial growth layer are reduced. If a thick GaN layer is grown on a base substrate such as sapphire using the FIELO method, and then the base substrate is removed, a high-quality GaN free-standing substrate with relatively few crystal defects can be obtained.

  In addition to the above, DEEP (Dislocation Elimination by the Epi-growth with Inverted-Pyramidal Pits) method has been developed as a method for obtaining a low-dislocation GaN free-standing substrate (see, for example, Non-Patent Document 2 and Patent Document 2). . In the DEEP method, by growing GaN using a mask made of silicon nitride or the like patterned on a GaAs substrate, a plurality of pits intentionally surrounded by facet surfaces are formed on the crystal surface, and dislocations are formed at the bottom of the pits. By accumulating, other regions are lowered in dislocation.

A GaN substrate obtained by growing a GaN film by a HVPE method on a heterogeneous substrate using such an ELO method or DEEP method, and then peeling the GaN layer from the underlying substrate requires a particularly low dislocation crystal. Although it is mainly used for the development of laser diodes (LD), it has recently been used as a substrate for LEDs.
JP-A-11-251253 JP 2003-165799 A Akira Usui et.al., "Thick GaN Epitaxial Growth with Low Dislocation Density by Hydride Vapor Phase Epitaxy", Jpn. J. Appl. Phys. Vol. 36 (1997) pp. L899-L902 Kensaku Motoki et.al., "Preparation of Large Freestanding GaN Substrates by Hydride Vapor Phase Epitaxy Using GaAs as a Starting Substrate", Jpn. J. Appl. Phys. Vol. 40 (2001) pp. L140-L143

  However, the as-grown GaN free-standing substrate obtained by the above method cannot be used as it is as a nitride-based semiconductor substrate because of its poor surface flatness and large substrate warpage. For this reason, it is general that the front and back surfaces of a GaN free-standing substrate are polished to a mirror finish before use in device fabrication.

  However, if the warp is large in the as-grown state, a large in-plane distribution is generated in the surface orientation after mirror polishing. When an LED or LD is manufactured using such a substrate, the surface orientation distribution directly affects the emission wavelength distribution, resulting in a significant loss of yield.

  Therefore, an object of the present invention is to solve the above-described problems, specifically, to reduce the variation in the plane orientation of the substrate surface by reducing the warpage of the substrate in the as-grown state. It is an object of the present invention to provide a group V nitride semiconductor substrate, a method of manufacturing the same, and a group III-V nitride semiconductor device excellent in in-plane uniformity using the substrate.

In order to achieve the above object, the group III-V nitride semiconductor substrate of the present invention is a self-supporting semiconductor substrate made of a group III-V nitride semiconductor crystal, and the rear surface has a dislocation density of 3 × 10 ⁶ cm. ⁻² or less, and the dislocation density is reduced at a rate of 3 × 10 ⁶ cm ⁻² / mm or less from the substrate back surface to the surface in the thickness direction.

The substrate thickness is preferably 100 μm or more and 10 mm or less. Further, the composition of the group III-V nitride-based semiconductor crystal can be expressed by In _x Ga _y Al _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). .

In order to achieve the above object, the method for producing a group III-V nitride semiconductor substrate of the present invention has a dislocation density of 3 × 10 3 in the thickness direction on a group III-V nitride semiconductor crystal on a different substrate. A step of depositing so as to decrease at a rate of ⁶ cm ⁻² / mm or less; a step of separating the group III-V nitride-based semiconductor layer from the dissimilar substrate; and the group III-V nitride-based semiconductor layer And a step of reducing the dislocation density so that the dislocation density is 3 × 10 ⁶ cm ⁻² or less with respect to the surface on the side where the different substrate is separated.

The step of depositing the III-V nitride semiconductor crystal is preferably performed by HVPE. Further, the composition of the group III-V nitride-based semiconductor crystal can be expressed by In _x Ga _y Al _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). .

  Further, in the step of reducing the dislocation density, the group III-V nitride semiconductor layer may be polished by a predetermined thickness from the surface on the side where the dissimilar substrate is separated.

  An epitaxial layer made of a group III-V nitride semiconductor crystal can be formed on the group III-V nitride semiconductor substrate to form a group III-V nitride semiconductor device. Examples of the III-V nitride semiconductor device include LD (laser diode), LED (light emitting diode), and HEMT (high electron mobility transistor).

  According to the group III-V nitride semiconductor substrate of the present invention, it is possible to reduce the warpage of the substrate in the as-grown state and to reduce the variation in the plane orientation of the substrate surface.

  Further, according to the method for producing a group III-V nitride semiconductor substrate of the present invention, a group III-V nitride semiconductor substrate with reduced variations in the plane orientation of the substrate surface can be obtained with certainty.

  Furthermore, according to the III-V nitride semiconductor device of the present invention, since a substrate with reduced variation in the plane orientation of the substrate surface is used, it has excellent in-plane uniformity and yield. Will improve.

  The group III-V nitride semiconductor substrate according to the present embodiment is a self-supporting GaN single crystal substrate obtained by growing a GaN-based semiconductor single crystal on a heterogeneous substrate and then peeling the GaN-based semiconductor single crystal. The dislocation density and the ratio of the dislocation density from the substrate back surface to the front surface in the thickness direction are within a specific range. Hereinafter, these points will be mainly described in detail.

(Independent substrate)
First, a self-supporting substrate (self-supporting substrate) refers to a substrate that not only can hold its own shape but also has a strength that does not cause inconvenience in handling. In order to have such strength, the thickness of the free-standing substrate is preferably 100 μm or more, more preferably 200 μm or more.

(Back side of substrate)
The back surface of the substrate is preferably polished flat. This is because the region having a high dislocation density is removed so as to fall within the range of the low dislocation density described later, and the adhesion between the substrate and the susceptor is improved when the substrate is epitaxially grown. If the entire back surface of the substrate is not evenly in contact with the susceptor, the heat conduction from the susceptor becomes non-uniform, and the substrate temperature during epi growth becomes non-uniform in the plane. In-plane variations in the substrate temperature appear as variations in crystal growth rate, composition, and impurity concentration, and it becomes impossible to grow epi with high in-plane uniformity of characteristics. Epi growth equipment also has a face-down method in which the back surface of the substrate is not in close contact with the susceptor, but in this case as well, it is common to place a flat plate called a soaking plate on the back surface of the substrate. If there is a variation in the distance between the soaking plate and the soaking plate, the aforementioned temperature variation occurs, resulting in a problem in the uniformity of characteristics.

  Further, the back surface (N surface) of the GaN substrate is easier to polish than the front surface (Ga surface), and the flattening polishing of the back surface does not increase the man-hour and decrease the yield as much as the front surface. The back surface need only be flat to such an extent that adhesion to the susceptor during epi growth can be obtained without any problem, and does not necessarily have to be a mirror surface. That is, it may be a lapping surface, a ground surface, or a surface subjected to a treatment for removing strain (etching or the like).

(Substrate surface)
The substrate surface of the GaN substrate does not need to be polished for the purpose of keeping it within a low dislocation density range or improving the adhesion between the substrate and the susceptor unlike the back surface of the substrate, but the as-grown state (crystal growth) In a state in which no processing step such as grinding or polishing is applied), a completely flat surface cannot be obtained. Since microfabrication is required for the device fabrication process, it is preferable to perform polishing on the substrate surface as well as on the back surface.

(Substrate conductivity type, carrier concentration)
The conductivity type of the substrate should be appropriately controlled according to the target device and cannot be determined uniformly. For example, n-type doped with Si, S, O, etc., or doped with Mg, Zn, etc. It can be p-type. Further, since the absolute value of the carrier concentration of the substrate should be appropriately controlled according to the target device, it cannot be determined uniformly. However, it is desirable that the LED substrate is a conductive substrate that can easily contact the back electrode, and for this purpose, the carrier concentration of the substrate is 5 × 10 ¹⁷ cm ⁻³ or more. It is desirable. However, if the carrier concentration of the substrate for the LED is too high, the crystallinity of the substrate is lowered and the transparency is impaired, so that it is 5 × 10 ¹⁷ cm ⁻³ or more and 1 × 10 ¹⁹ cm. It is more desirable to control to ^-3 or less.

(Dislocation density of substrate)
When GaN is grown on a heterogeneous substrate by the ELO method, the FIELO method, or the like, dislocations are greatly reduced at the initial stage of growth (about 30 μm), and thereafter, defects generally slowly decrease. Finally, if there is a large difference in dislocation density between the back surface and the front surface of the substrate, a difference occurs in the lattice spacing, which causes the substrate to warp. For this reason, (1) the region where there are many dislocations in the initial stage of growth is removed by polishing, and the dislocation density on the back surface is 3 × 10 ⁶ cm ⁻² or less in the state after mirror polishing of the back surface. (2) By controlling the growth conditions of the region where defects are slowly reduced, the difference in dislocation density per unit length in the thickness direction of the substrate is 3 × 10 ⁶ cm ⁻² / mm or less, thereby warping in as-grown. As shown in the results of Examples to be described later, it is possible to significantly improve the yield.

If the above conditions (1) and (2) are satisfied, for example, when the dislocation density changes by 1 × 10 ⁶ cm ⁻² at a thickness of 250 μm near the substrate surface (that is, 4 × 10 ⁶ cm ⁻² per 1 mm). A sudden drop in the dislocation density as in the case of a change in position is eliminated, and the warpage in as-grown does not increase, so that the variation in plane orientation does not change much. Furthermore, at present, there is no GaN substrate that has achieved a low dislocation density of 10 ⁴ cm ⁻² on the entire surface of the substrate, but the dislocation density on the back surface of the substrate is 3 × 10 ⁶ cm ^−2. Is ideally 0, this is a case where the maximum dislocation density is 3 × 10 ⁶ times different. If the thickness is 1 mm or more, the conditions (1) and (2) are satisfied. Variation will be obtained.

(Substrate material)
As a material for the substrate of the present embodiment, not only GaN but also the general formula: In _x Ga _y Al _1-xy N (where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1) III-V group nitride semiconductors represented by As the group III-V nitride semiconductor crystal, GaN, AlN, InN, and mixed crystals thereof are practically used. From the viewpoint of a substrate, GaN can easily obtain a crystal having a large diameter and a large thickness, and homoepitaxial growth is easy, but other than this, substrates of AlN or AlGaN are also available. It is advantageous in terms of usability. Further, these substrate surfaces are preferably (0001) group III surfaces. This is because the GaN-based crystal has a strong polarity, the group III surface is more chemically and thermally stable than the group V surface (nitrogen surface), and the device can be easily manufactured.

(Substrate manufacturing method)
The substrate of this embodiment is obtained by growing a GaN-based semiconductor single crystal on a different substrate and then peeling it.
The GaN-based semiconductor single crystal is desirably grown by HVPE (hydride vapor phase epitaxy). This is because the HVPE method has a high crystal growth rate and is suitable for manufacturing a substrate that requires thick film growth. Further, as a method of peeling a GaN-based semiconductor single crystal after it has been grown, a void formation peeling method (VAS method) can be used. The VAS method is excellent in that a large-diameter substrate can be peeled off with good reproducibility, and a GaN-based free-standing substrate having low dislocations and uniform characteristics can be obtained. The method of growing a GaN-based semiconductor single crystal on a heterogeneous substrate and then peeling it off is currently used to grow a GaN-based free-standing substrate having a diameter of φ2 inches or more and a sufficient thickness to withstand handling. This is because the method is limited to a method in which the laser lift-off method is combined with the VAS method or the FIELO method.

(GaN device)
The GaN free-standing substrate of this embodiment is suitable for applications in which a III-V nitride semiconductor crystal is epitaxially grown on the GaN substrate by MOVPE to produce a short wavelength LD, LED, and high voltage HEMT. In the GaN free-standing substrate of this embodiment, variation in the plane orientation is reduced. By using the substrate to manufacture a short wavelength LD or LED, an LD or LED having a uniform in-plane distribution of emission wavelengths can be obtained. Obtainable. Further, in a high-frequency device such as HEMT, there is a possibility that a difference occurs in the incorporation of impurities that give conductivity accumulated at the epi-substrate interface due to variations in the plane orientation of the substrate surface. By using this, it is possible to stabilize the buffer leak by suppressing variations in the plane orientation, and in combination with various measures for reducing impurities, it is possible to provide a high-performance HEMT epi with low leakage and small variations.

(Manufacture of GaN free-standing substrates)
A GaN free-standing substrate was manufactured by the manufacturing process shown in FIG.
First, on the C-plane sapphire substrate 1 having a diameter of 2 inches, the Si-doped GaN layer 3 was grown by 0.5 μm through a 20 nm low-temperature growth GaN buffer layer by the MOVPE method (a). The growth conditions were normal pressure, substrate temperature during buffer layer growth of 600 ° C., and substrate temperature during epi layer growth of 1100 ° C. The raw materials used were TMG as a group III raw material, NH ₃ as a group V raw material, and monosilane as a dopant. The carrier gas is a mixed gas of hydrogen and nitrogen. The crystal growth rate was 4 μm / h. The carrier concentration of the epi layer was 2 × 10 ¹⁸ cm ⁻³ .

Next, a metal Ti thin film 5 was deposited on the Si-doped GaN layer 3 to a thickness of 20 nm (b). The substrate thus obtained was placed in an electric furnace and heat-treated at 1050 ° C. for 20 minutes in a H ₂ stream containing 20% NH ₃ . As a result, a part of the GaN layer 3 is etched to generate a high-density void layer (void layer) 6, and the Ti layer is nitrided to form submicron fine holes on the surface with high density TiN Changed to layer 7 (c).

This substrate was put into an HVPE furnace, and a GaN layer 8 was formed in a thickness of 600 μm using a supply gas containing a source gas composed of 8 × 10 ⁻³ atm GaCl and 4.8 × 10 ⁻² atm NH _{3 in} a carrier gas. Grow to thickness (d). Here, N ₂ gas containing 5% of H ₂ was used as the carrier gas. The growth conditions for the GaN layer were normal pressure and a substrate temperature of 1080 ° C. In the GaN crystal growth process, Si was doped by supplying SiH ₂ Cl ₂ as a doping source gas to the substrate region. After the growth was completed, in the process of cooling the HVPE apparatus, the GaN layer 8 naturally separated from the base substrate with the void layer 6 as a boundary, and a GaN free-standing substrate was obtained.

  The obtained GaN free-standing substrate 9 was warped in a convex direction on the back surface side, and the front surface was a concave shape reflecting the shape of the warp on the back surface (e). Next, both surfaces were polished so that the GaN free-standing substrate 9 can be used as a substrate for a nitride-based semiconductor element. Polishing was performed from the back side. The back surface (N surface) is polished by grinding, but may be performed by lapping (using GC # 800 or the like). As an example, the GaN free-standing substrate 9 was polished to a thickness of about 150 μm to 300 μm. Thereafter, the back surface was etched using a NaOH aqueous solution or a mixed solution of hydrochloric acid and hydrogen peroxide. For example, the mixed solution used was a mixed solution mixed at a ratio of hydrochloric acid: hydrogen peroxide solution: water = 1: 1: 2. After etching, the back surface roughness was several μm to several hundred nm. After the back surface etching, polishing was performed after lapping in order to mirror the surface (Ga surface) of the GaN free-standing substrate. Further, the surface was polished in the same process, and the GaN free-standing substrate 10 was obtained (f).

The dislocation density of the back surface and the front surface of this substrate (No. 1) was 8.1 × 10 ⁶ and 4.3 × 10 ⁶ cm ⁻² , respectively, and the dislocation density ratio between the back surface and the front surface was 1.9. Moreover, the dislocation density difference per unit thickness was 7.6 × 10 ⁶ cm ⁻² / mm. The obtained results are shown in Table 1.

  In the same manner as described above, a GaN free-standing substrate was manufactured by the manufacturing process shown in FIG.

  In the same manner as described above, a GaN free-standing substrate was manufactured by the manufacturing process shown in FIG.

(Manufacture of GaN-based light emitting devices)
No. obtained A GaN-based light emitting device was manufactured on the GaN free-standing substrate 1 to 3 using a reduced pressure MOVPE method.

  FIG. 2 shows the structure of the manufactured GaN-based light emitting device. This light emitting device has a multi-quantum well structure 20 composed of three InGaN well layers 21 and four GaN barrier layers, a p-type AlGaN cladding layer 23 doped with Mg, and Mg doped on a GaN free-standing substrate 10. The p-type GaN contact layer 24 is sequentially laminated, and an n-type electrode 25 is formed on the back surface of the GaN free-standing substrate 10, and a p-type electrode 26 is formed on the surface of the p-type GaN contact layer 24.

This GaN-based light emitting device is formed by using a known metal organic chemical vapor deposition (MOCVD) method as an organic metal raw material, such as trimethyl gallium (TMG), trimethyl aluminum (TMA), trimethyl indium (TMI), biscyclopentadienyl magnesium ( Cp ₂ Mg) was manufactured as follows using ammonia (NH ₃ ) and silane (SiH ₄ ) as gas raw materials and hydrogen and nitrogen as carrier gases.

First, no. A multi-quantum well structure (MQW) comprising three In _0.15 Ga _0.85 N well layers 21 having a thickness of 3 nm and four GaN barrier layers 22 having a thickness of 10 nm on one GaN free-standing substrate 10. An InGaN-based active layer having 20) was formed. At this time, the growth was interrupted after the respective well layers and barrier layers were formed. The growth interruption was performed by temporarily stopping the supply of Group III materials such as TMG and TMI. Next, a p-type Al _0.1 Ga _0.9 N clad layer 23 and a p-type GaN contact layer 24 were formed in this order on the multiple quantum well structure 20. Finally, an n-type electrode 25 was formed on the back surface (N surface) side of the GaN free-standing substrate 10, and a p-type electrode 26 was formed on the p-type GaN contact layer 24.

  Next, no. Similarly, GaN-based light emitting devices were manufactured on a few GaN free-standing substrates, and the yield rates were compared. The thickness of the GaN substrate is set to 500 μm. The results are shown in Table 2.

The absolute value of the yield rate varies depending on the epi structure, the growth method, and the standard. As a result of comparison under the same conditions, as shown in Table 2, the rear surface dislocation density is 3 × 10 ⁶ cm ⁻² or less, and the unit It has been found that when the dislocation density difference per thickness is 3 × 10 ⁶ cm ⁻² / mm or less, significant yield improvement can be achieved.

[Other Embodiments]
As described above, the present invention has been described in detail based on the embodiments. However, these are exemplifications, and various modifications can be made to combinations of these processes, and such modifications are also within the scope of the present invention. This will be understood by those skilled in the art. For example, in the examples, the GaN crystal growth is performed by the HVPE method, but the MOVPE method may be combined with a part of the GaN crystal growth.

  In the above embodiment, the effect in the LED structure was verified, but the same effect is also estimated in the LD structure including MQW.

In addition, in order to cause the growth to occur while projecting a plurality of irregularities at the crystal growth interface at an initial stage or in the middle of the crystal growth, a known ELO technique using a mask such as SiO ₂ may be used in combination.

In the embodiments, a sapphire substrate is used as the base substrate, but any substrate that has been reported as a conventional GaN-based epitaxial layer substrate, such as GaAs, Si, ZrB ₂ , or ZnO, can be applied.

  Further, in the examples, a method for producing a Si-doped GaN free-standing substrate was illustrated, but the GaN free-standing substrate doped with undoped or other dopants such as Mg, Fe, S, O, Zn, Ni, Cr, Se, etc. It can also be applied.

  Moreover, although the manufacturing method of the GaN self-supporting substrate was illustrated in the embodiment, it can be applied to AlN, AlGaN, InGaN, and AlInGaN substrates.

6 is a schematic diagram showing a method for manufacturing a GaN free-standing substrate according to Example 1. FIG. 6 is a cross-sectional view showing a GaN-based light emitting device according to Example 2. FIG.

Explanation of symbols

1 sapphire substrate 3 Si-doped GaN layer 5 Ti thin film 6 void layer 7 TiN layer 8 GaN layer 9 GaN free-standing substrate 10 GaN free-standing substrate 20 multiple quantum well structure 21 InGaN well layer 22 GaN barrier layer 23 p-type AlGaN cladding layer 24 p-type GaN contact layer 25 n-type electrode 26 p-type electrode

Claims (8)

A self-supporting semiconductor substrate made of a III-V nitride-based semiconductor crystal, the dislocation density on the back surface of the substrate being 3 × 10 ⁶ cm ⁻² or less, and the dislocation density from the back surface to the front surface in the thickness direction Is reduced at a rate of 3 × 10 ⁶ cm ⁻² / mm or less, a group III-V nitride-based semiconductor substrate.   2. The group III-V nitride semiconductor substrate according to claim 1, wherein the substrate thickness is 100 μm or more and 10 mm or less. The composition of the III-V nitride semiconductor crystal is represented by In _x Ga _y Al _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). The group III-V nitride semiconductor substrate according to claim 1. Depositing a group III-V nitride-based semiconductor crystal on a heterogeneous substrate so that the dislocation density decreases at a rate of 3 × 10 ⁶ cm ⁻² / mm or less in the thickness direction;
Separating the III-V nitride-based semiconductor layer and the heterogeneous substrate;
Reducing the dislocation density such that the dislocation density is 3 × 10 ⁶ cm ⁻² or less with respect to the surface of the group III-V nitride-based semiconductor layer on which the heterogeneous substrate is separated;
A method for producing a group III-V nitride semiconductor substrate, comprising:   The method of manufacturing a group III-V nitride semiconductor substrate according to claim 4, wherein the step of depositing the group III-V nitride semiconductor crystal is performed by an HVPE method. The composition of the III-V nitride semiconductor crystal is represented by In _x Ga _y Al _1-xy N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1). A method for producing a group III-V nitride semiconductor substrate according to claim 4.   5. The step of reducing the dislocation density comprises polishing the group III-V nitride semiconductor layer by a predetermined thickness from the surface on the side where the different substrate is separated. The manufacturing method of the group III-V nitride type semiconductor substrate of description.   A group III-V nitride system in which an epitaxial layer made of a group III-V nitride semiconductor crystal is formed on the group III-V nitride semiconductor substrate according to any one of claims 1 to 3. Semiconductor device.

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