JP6249250B2 - Group III nitride semiconductor and method of manufacturing the same - Google Patents

Description

  The present invention relates to a group III nitride semiconductor and a manufacturing method.

Conventionally, a method for manufacturing a GaN-based laser element using a ScAlMgO ₄ substrate is known (see, for example, Patent Document 1). ScAlMgO ₄ has a lattice constant mismatch (mismatch rate (lattice constant of GaN−lattice constant of ScAlMgO ₄ ) / lattice constant of GaN) of −1.9% with GaN, and the mismatch rate of the sapphire substrate ( + 16%). Therefore, when GaN is crystal-grown using the ScAlMgO ₄ substrate as a seed substrate, a GaN crystal having a smaller defect density than that of the sapphire substrate can be obtained. Patent Document 1, after forming a buffer layer of amorphous or polycrystalline at a low temperature of about 600 ° C. to ScAlMgO ₄ on the substrate, a metal organic chemical vapor deposition method (M etal O rganic C hemical V apor D eposition: less MOCVD method Shows a method of forming a GaN single crystal thin film at a high temperature of 1050 ° C.

Patent Document 2 discloses a technique in which a mask is formed in a partial region of a different substrate different from GaN, such as a sapphire substrate, and a GaN crystal is selectively grown in the lateral direction on the mask. In Patent Document 2, a GaN crystal is grown on a sapphire substrate or a ScAlMgO ₄ substrate at a temperature of about 650 to 690 ° C. by an ammonothermal lateral epitaxial growth method.

JP-A-2015-178448 JP 2014-1111527 A

However, both of the techniques of Patent Document 1 and Patent Document 2 have a problem that lattice constant mismatch exists and stress is concentrated on the interface between the grown crystal and the seed substrate. Stress concentration at the interface causes crystal quality degradation such as crystal axis inclination and warpage. For this reason, it is a subject to obtain a group III nitride semiconductor containing a group III nitride crystal of higher quality than before, and realization of the manufacturing method.
The present invention solves the above-described problems, and an object thereof is to provide a high-quality group III nitride semiconductor and a method for manufacturing the same.

To achieve the above object, the present disclosure provides a single crystal represented by the general formula RAMO ₄ (in the general formula, R is one selected from the group consisting of Sc, In, Y, and a lanthanoid element) Or A represents a plurality of trivalent elements, A represents one or more trivalent elements selected from the group consisting of Fe (III), Ga, and Al, and M represents Mg, Mn, Fe ( II), Co, Cu, Zn, and the RAMO ₄ substrate consisting represents one or more divalent elements) selected from the group consisting of Cd, it is formed on the RAMO ₄ substrate, the RAMO ₄ substrate A heterogeneous film made of a different material and having a plurality of openings, formed on the heterogeneous film and in the opening of the heterogeneous film, made of a different material from the heterogeneous film, and M in the general formula The element represented by And a group III nitride crystal containing the group III nitride semiconductor.

  According to the present disclosure, it is possible to provide a group III nitride semiconductor including a high quality group III nitride crystal and a method for manufacturing the same.

Cross-sectional view of group III nitride semiconductor process according to an embodiment of the present disclosure Cross-sectional schematic diagram of a group III nitride semiconductor according to a modification of the embodiment of the present disclosure Cross-sectional schematic diagram of a group III nitride semiconductor according to an embodiment of the present disclosure The graph which shows the profile which measured the element concentration in the group III nitride crystal by embodiment of this indication by secondary ion mass spectrometry Graph showing the dependence of the lattice constant (a-axis lattice constant) on Mg atom concentration when GaN is doped with Mg

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment)
A group III nitride semiconductor 100 according to the present disclosure is shown in FIG. The group III nitride semiconductor 100 includes a RAMO ₄ substrate 001 made of a substantially single crystal represented by the general formula RAMO ₄ , and the group III nitride crystal 004 is formed on the RAMO ₄ substrate 001 via a heterogeneous film 002. Are stacked. In the present embodiment, when the group III nitride semiconductor is manufactured, a part of the group III nitride crystal 004 is epitaxially grown using the RAMO ₄ substrate 001 as a seed substrate. In the above general formula, R represents one or more trivalent elements selected from Sc, In, Y, and a lanthanoid element (atomic number 67-71), and A represents Fe (III), Ga , And one or more trivalent elements selected from Al, wherein M is one or more divalent elements selected from Mg, Mn, Fe (II), Co, Cu, Zn, and Cd Represents an element. Further, the substantially single crystal of RAMO _4, RAMO ₄ constituting the surface (epitaxial growth surface) of epitaxially growing group III nitride contains more than 90 at%, and when focusing on any crystal axis, the epitaxial growth surface A crystalline solid whose orientation is the same in any part. However, those in which the direction of the crystal axis is locally changed and those containing local lattice defects are also treated as single crystals. In the above general formula, O is oxygen. In the above general formula, R is preferably Sc, A is Al, and M is Mg.

  The group III element metal constituting the group III nitride crystal is most preferably gallium (Ga), but may be aluminum (Al), indium (In), thallium (Tl), or the like. In the present embodiment, the group III nitride crystal contains an element represented by M in the above general formula. In addition, it is not necessary for all group III nitride crystals to contain the element represented by M, and it is sufficient that the element is partially contained.

Hereinafter, the case where R in the above general formula is Sc, A is Al, and M is Mg, that is, RAMO ₄ is ScAlMgO ₄ and the group III nitride is GaN will be described as an example. The present invention is not limited to the embodiment.

As described above, the group III nitride semiconductor 100 of the present embodiment has the ScAlMgO ₄ substrate 001 made of a ScAlMgO ₄ single crystal (see FIG. 3). On the ScAlMgO ₄ substrate 001, a dissimilar film (hereinafter also referred to as “mask layer”) 002 made of a material different from that of the ScAlMgO ₄ substrate 001 and having a plurality of openings 008 is disposed. Mask layer 002 includes a plurality of convex portions 009 which covers the ScAlMgO ₄ substrate 001, it is formed between the convex portion 009, and a plurality of apertures 008 which ScAlMgO ₄ substrate 001 is exposed. A GaN crystal 004 made of a material different from that of the mask layer 002 is disposed on the mask layer 002.

In the group III nitride semiconductor 100 of this embodiment, since forming the GaN crystal 004 through the mask layer 002 on ScAlMgO ₄ substrate 001, even with ScAlMgO ₄ substrate 001 as a seed substrate, a high quality A GaN crystal 004 can be formed.

Here, the mask layer 002 is preferably in direct contact with the ScAlMgO ₄ substrate 001. Mask layer 002 and in contact with ScAlMgO ₄ substrate 001, within the opening 008 of the mask layer 002, it is possible to epitaxially grow a GaN of ScAlMgO ₄ substrate 001 as a seed substrate.

  Here, the convex part 009 of the mask layer 002 is preferably made of a dielectric or metal. When the convex part 009 is made of a dielectric or metal, GaN can be selectively grown in the vapor phase growth method of GaN, and a high-quality GaN crystal can be obtained.

  Specific examples of the dielectric constituting the convex portion 009 of the mask layer 002 include silicon nitride, silicon oxide, silicon oxynitride, aluminum oxide, aluminum nitride oxide, titanium oxide, zirconium oxide, and niobium oxide. It may be used independently and two or more types may be used together.

  In particular, the convex portion 009 of the mask layer 002 is preferably made of a refractory metal or a refractory metal compound. In the vapor phase growth method such as MOCVD for forming the GaN crystal 004, crystal growth is generally performed at a high temperature (for example, about 1000 ° C.). A refractory metal or a refractory metal compound is used in such a high temperature atmosphere. It is difficult to decompose and hardly generate impurities. Specific examples of the refractory metal or the refractory metal compound include tungsten, molybdenum, niobium, tungsten silicide, molybdenum silicide, and niobium silicide. These may be used alone or in combination of two or more. Also good.

  The film thickness of the convex part 009 of the mask layer 002 is desirably 10 nm or more and 100 nm or less. If there is a region thinner than 10 nm, GaN may be difficult to selectively grow. On the other hand, if the film thickness of the convex part 009 is larger than 100 nm, when the GaN crystal 004 grows in the lateral direction, voids or defects may be generated in a region in contact with the convex part 009, and the quality of the GaN crystal 004 deteriorates. There is.

  The width of the convex part 009 is preferably wide. When the width of the convex part 009 is wide, the area of the GaN crystal 004 with few defects formed on the convex part 009 is sufficiently large. Specifically, the width of the convex part 009 is desirably 3 μm or more and 30 μm or less.

  On the other hand, the width of the opening 008 is preferably 1 μm or more and 100 μm or less. If the width of the opening 008 is too wide, the width of the convex part 009 is relatively narrow, and the area of the GaN crystal 004 with few defects formed on the convex part 009 is narrowed. In this case, the defect reduction effect is reduced. On the other hand, if the width of the opening 008 is too narrow, it becomes difficult to form a sufficiently large GaN crystal in the opening 008.

  The shape of the convex part 009 is not particularly limited as long as the mask layer 002 is provided with a plurality of openings 008. For example, the convex part 009 may have a stripe shape or other shapes. Further, the shape of the opening 008 is not particularly limited, and may be, for example, a stripe shape or a dot shape. However, it is preferable that the openings 008 are periodically arranged between the convex portions 009.

Here, the GaN crystal 004 is preferably in direct contact with the ScAlMgO ₄ substrate 001 through the plurality of openings 008. When these are in direct contact, GaN can be epitaxially grown using the ScAlMgO ₄ substrate 001 as a seed substrate. In this embodiment, since the mask (convex portion 009) is partially formed, the GaN crystal 004 and the ScAlMgO ₄ substrate 001 are only in partial contact. Therefore, the stress generated at these interfaces is reduced as compared with the case where they are in contact with each other. As a result, the GaN crystal 004 is hardly warped, and further, the generation of interface defects is suppressed. Such a GaN crystal 004 can be used as a template of a higher quality group III nitride crystal.

Next, the manufacturing method of the group III nitride semiconductor 100 of this Embodiment is demonstrated using FIG.
First, a step of preparing a ScAlMgO ₄ substrate 001 which is a single crystal is performed (FIG. 1A), and then a step of depositing a layer 002a made of a mask layer material on the ScAlMgO ₄ substrate 001 is performed (FIG. 1). (B)) Next, a resist film 003 is applied to the upper surface of the layer 002a (FIG. 1C), and the applied resist film is patterned in a stripe shape by a photolithography method (FIG. 1D). In this step, a resist pattern 013 is formed on the layer 002a.

  Thereafter, a step of removing a part of the layer 002a by etching (FIG. 1E) and a step of removing the remaining resist pattern 013 (FIG. 1F) are performed. Thus, a mask layer 002 having a plurality of stripe-shaped convex portions 009 and a plurality of openings 008 is formed. The etching method is not particularly limited, and can be dry etching, for example. In addition, the mask layer 002 formed in this embodiment has a pattern including an opening 008 portion having a cross-sectional width of about 3 μm and a convex portion 009 having a cross-sectional width of about 12 μm.

Next, a step of forming a GaN crystal 004 on the mask layer 002 is performed (FIG. 1 (g) and FIG. 1 (h)). As a method for forming the GaN crystal 004, for example, a metal organic chemical vapor deposition method (hereinafter referred to as MOCVD method) can be used. In the MPCVD method, GaN is crystal-grown under a high temperature atmosphere of about 900 to 1000 ° C. In this embodiment mode, trimethyl gallium (TMGa) and ammonia are used as raw materials. A mixed gas of hydrogen and nitrogen is used as the carrier gas. Strictly speaking, in this step, GaN is crystal-grown starting from the ScAlMgO ₄ substrate 001 exposed in the plurality of openings 008 of the mask layer 002. That is, the GaN crystal 004 is formed so as to be in direct contact with the ScAlMgO ₄ substrate 001. However, as the crystal growth proceeds, the GaN crystal 004 comes into direct contact with the convex portion 009 of the mask layer 002. When the GaN crystal 004 further grows, the GaN crystal 004 extends in the lateral (plane) direction on the upper surface of the convex portion 009 of the mask layer 002. Thereby, a plurality of GaN crystals 004 having a thin film structure are formed (FIG. 1G).

When a plurality of GaN crystals 004 having a thin film structure are further grown, adjacent GaN crystals 004 are coupled and integrated with each other at a coupling portion 006 located substantially at the center of the convex portion 009 (FIG. 1 (h)). A GaN crystal 004 made of a single crystal is formed on the ScAlMgO ₄ substrate 001, and a GaN semiconductor having a high-quality GaN crystal 004 is manufactured.

Here, the reason why the group III nitride crystal of the group III nitride semiconductor manufactured by this method is of high quality will be described below.
As described above, the lattice constant of GaN is smaller than that of ScAlMgO ₄ . For this reason, a lattice mismatch rate of −1.9% exists between the ScAlMgO ₄ substrate 001 and the GaN crystal 004. For this reason, defects 313 (threading dislocations) occur in the GaN crystal 004 formed in the vicinity of these interfaces. The defect 313 propagates substantially parallel to the growth direction of the GaN crystal 004. Accordingly, when GaN is grown as in this embodiment, the defects 313 are concentrated in the vicinity of the opening 008 of the mask layer 002. On the other hand, dislocations 313 are difficult to propagate to the GaN crystal 004 grown laterally on the convex part 009 of the mask layer 002. That is, the defect 313 can be locally concentrated near the opening 008 of the mask layer 002, and a high-quality crystal with few defects 313 can be obtained outside the region.

  When sapphire is used as a seed substrate and GaN is heteroepitaxially grown, the absolute value of the lattice mismatch rate between sapphire and GaN is as large as 16%. Therefore, even if a mask layer is formed on a sapphire substrate which is a seed substrate and a GaN crystal is grown as in this embodiment, it is difficult to suppress dislocation propagation. That is, when sapphire or the like is used as a seed substrate, it is essential to further provide a low-temperature buffer layer such as amorphous AlN between the substrate and the mask layer.

On the other hand, when the ScAlMgO ₄ substrate is used as the seed substrate as in this embodiment, a high-quality crystal can be produced as described above even if the mask layer 002 is formed directly on the ScAlMgO ₄ substrate 001. Can do. In other words, when performing heteroepitaxial growth of GaN (Group III nitride crystal), it is not always necessary to provide a low-temperature buffer layer such as amorphous AlN, and higher quality GaN (Group III nitride) crystal can be formed efficiently. can do.

Next, the technical significance of the group III nitride semiconductor manufacturing method of the present embodiment will be described in more detail with reference to FIG. As described above, in the manufacturing method of the present embodiment, the mask layer 002 having the plurality of openings 008 is formed on the ScAlMgO ₄ substrate 001. Then, a GaN crystal 004 is grown using the ScAlMgO ₄ substrate 001 exposed in the plurality of openings 008 of the mask layer 002 as a starting point. When the GaN crystal 004 is grown, a plurality of minute GaN crystals 004 are selectively grown in the lateral direction, and adjacent GaN crystals 004 are combined near the center of the convex part 009. Further, when the GaN crystal 004 grows, a flat crystal plane grows in the c-axis direction. Note that the surface of the GaN crystal 004 (the side opposite to the ScAlMgO ₄ substrate 001) is a c-plane. The film thickness of the GaN crystal 004 can be set to 5 μm, for example.

As described above, in the GaN crystal 004 obtained by the manufacturing method of the present embodiment, the defects 313 are concentrated in the central region of the plurality of openings 008, and a region 317 with many defects is formed. On the other hand, a region 318 with few defects is formed in the region above the convex portion 009 of the mask layer 002. In the regions 318 with few defects in the GaN crystal 004, the influence of the lattice mismatch between the ScAlMgO ₄ substrate 001 and the GaN crystal 004 is small, and they can be smoothly combined without warping or tilting. Therefore, almost no new defects are generated in this region 318. For this reason, excluding the vicinity of the opening 008 of the mask layer 002, the dislocation density of the GaN crystal 004 can be 1 × 10 ⁶ m ⁻² or less.

Here, when GaN is grown by MOCVD in a high temperature atmosphere of about 900 to 1000 ° C., Mg atoms in the ScAlMgO ₄ substrate 001 are partially decomposed and evaporated to diffuse into the GaN crystal 004. For the ScAlMgO ₄ substrate 001 in the vicinity of the opening 008 of the mask layer 002 (region represented by 320 in FIG. 3) and the GaN crystal 004 in the opening 008, the profile of Mg concentration in the depth direction is analyzed by secondary ion mass spectrometry (SIMS). ; The result measured by Secondary Ion Mass Spectrometry) is shown in FIG. As shown in FIG. 4, the Mg concentration of the GaN crystal 004 in the opening 008 (Mg concentration in the region 317 in FIG. 3) is 7 × 10 ¹⁷ [atoms / cm ³ ] or more. It can be seen that is included. Further, as shown in FIG. 4, the closer to the ScAlMgO ₄ substrate 001, the higher the Mg concentration, and it can be said that Mg atoms are diffused from the ScAlMgO ₄ substrate 001. When the Mg concentration of the GaN crystal 004 in the opening 008 exceeds 5 × 10 ²¹ [atoms / cm ³ ], the calculated lattice constant increases, but the Mg concentration for substituting the group III element is the group III nitride crystal. This causes a problem that the crystal quality of the group III nitride semiconductor itself is deteriorated. Therefore, the Mg concentration is preferably 7 × 10 ^{17 to} 5 × 10 ²¹ [atoms / cm ³ ].

  For the GaN crystal 004 formed on the convex portion 009 of the mask layer 002 (region 318 in FIG. 3), the Mg concentration was measured in the same manner. As a result, the region GaN crystal 004 contained no Mg atoms. A substantial diffusion of atoms was not observed.

When a certain amount (for example, 7 × 10 ^{17 to} 5 × 10 ²¹ [atoms / cm ³ ]) of Mg atoms is mixed in the region 317, the lattice constant of the GaN crystal 004 formed in the region increases. . As a result, the lattice constant of the GaN crystal 004 is comprised closer to the lattice constant of _{ScAlMgO 4} substrate 001, is reduced stress at the interface between the GaN crystal 004 and ScAlMgO ₄ board 001, tilt or warping of the crystal axis is small. That is, as in the present embodiment, by employing the MOCVD method in which crystal growth is performed at a high temperature, the GaN crystal 4 with less warpage and crystal axis inclination can be formed in the region 317.

Furthermore, it is more preferable that the Mg concentration of the GaN crystal 004 in the opening 008 is 1 × 10 ^{20 to} 5 × 10 ²¹ [atoms / cm ³ ]. The reason for this will be described with reference to the Mg atom concentration dependence graph of the lattice constant (a-axis lattice constant) when GaN is doped with Mg as shown in FIG. This graph is obtained by the inventors calculating the average lattice constant based on the bond length value between Ga and Mg when Mg substitutes the Ga atom position in the GaN crystal. In calculating the change in the bond length between Ga and N, the charge of Ga at the Ga site in the GaN crystal is assumed to be 0 (neutral). Further, the lattice constant of this graph is the lattice constant in the c-plane (0001) plane for crystal growth (lattice constant in the direction perpendicular to the c-axis). According to this, it can be seen that when the Mg concentration in the GaN crystal is 1 × 10 ²⁰ [atoms / cm ³ ] or more, the lattice constant of GaN is significantly increased. Therefore, by setting the Mg concentration of the GaN crystal 004 to 1 × 10 ^{20 to} 5 × 10 ²¹ [atoms / cm ³ ], the difference in lattice constant between the seed substrate and the group III nitride crystal grown on the seed substrate can be reduced. It is possible to obtain a group III nitride having a good crystal quality while making it smaller.

Here, dislocations (defects 313) generated from the interface with the ScAlMgO ₄ substrate 001 are concentrated in the GaN crystal in the region 317, and the diffusion of Mg atoms is promoted through the dislocations. As a result, the GaN crystal 004 in the entire region in contact with the ScAlMgO ₄ substrate 001 has a larger lattice constant than other regions. Such a GaN crystal 004 is less likely to warp even when grown to a thick film.

  On the other hand, in the region other than the region 317 in FIG. 3, that is, the region 318 adjacent to the region 317, Mg diffusion hardly occurs. Therefore, the Mg concentration in the region is substantially zero. This is reported, for example, in Japanese Journal of Applied Physics No. 44 (2005), pages 6495-6504, when there is no dislocation, the diffusion coefficient of atoms is reported to be reduced by about three orders of magnitude compared to the case with dislocation. This is supported by the fact that Therefore, it can be determined that Mg diffusion does not substantially occur in the GaN crystal 004 adjacent to the region 317 (a GaN crystal in a region other than the region 317).

Here, when the crystal is further grown for the GaN crystal 004 in which Mg is diffused, dislocations converge and the diffusion of Mg atoms is gradually suppressed. Then, it approaches a GaN template having a uniform lattice constant. That is, in the GaN crystal 004 in the region 317 in FIG. 3, the Mg concentration on the ScAlMgO ₄ substrate side is high and the Mg concentration on the opposite surface is low.

Based on the above, when a group III nitride semiconductor is manufactured by the manufacturing method of the present embodiment, a divalent atom (in this embodiment) contained in the RAMO ₄ substrate is included in a part of the group III nitride crystal (GaN crystal). In the embodiment, it is possible to partially include Mg atoms of the ScAlMgO ₄ substrate in the group III nitride crystal. Such a group III nitride crystal including a divalent atom in part has a lattice constant close to that of the RAMO ₄ substrate, and is less warped and tilted in the crystal axis. Then, a group III nitride semiconductor having a high-quality group III nitride crystal with few defects is obtained by further growing the crystal using a group III nitride crystal containing a divalent atom in a part as a template. .

In the conventionally disclosed ammonothermal lateral epitaxial growth, the temperature at which the GaN crystal is grown is as low as about 650 to 690 ° C. Therefore, even when GaN is crystal-grown using the ScAlMgO ₄ substrate, Mg atoms hardly diffuse into the GaN crystal 004. For example, when the diffusion coefficient is calculated using the activation energy of Mg diffusion in GaN of Solid-State Electronics 43 (1999) pages 621 to 623, it is compared with the Mg diffusion coefficient during GaN growth by MOCVD method. The Mg diffusion coefficient during GaN growth by the method is about 10 to 30 times smaller. Therefore, when a GaN crystal is grown by the ammonothermal method, substantially no Mg diffusion occurs. Therefore, Mg is not substantially contained in the GaN crystal grown by the ammonothermal lateral epitaxial growth of the conventional disclosure.

Here, when the GaN crystal is manufactured by the above-described method, the dislocation density of the GaN crystal in the region 318 can be 1 × 10 ⁶ m ⁻² or less, whereas the GaN crystal is not provided with the mask layer 002. When the crystal was grown, the dislocation density of the GaN crystal (film thickness was about 2 μm) was about 3 to 5 × 10 ⁷ cm ⁻² . Further, when GaN was epitaxially grown using a sapphire substrate as a seed substrate instead of the ScAlMgO ₄ substrate, the dislocation density of the grown GaN crystal further increased by about 1 to 2 digits.

The dislocations in the GaN crystal are introduced due to the lattice mismatch of the seed substrate and the thermal expansion mismatch with respect to the GaN crystal to be grown (group III nitride crystal). Therefore, as long as it is heteroepitaxy, it is difficult to completely eliminate dislocations. Here, when the dislocation density of GaN exceeds 1 × 10 ⁷ cm ⁻² , the quality becomes insufficient as a substrate for light emitting diodes or laser diodes for lighting or automobile headlights. For this reason, a GaN crystal having a dislocation density of 1 × 10 ⁶ m ⁻² or less is desired in practical use, and the group III nitride semiconductor according to the present embodiment can satisfy this demand.

(Modification)
The group III nitride semiconductor of the present disclosure includes an Al _x Ga _1-x N layer 007 (0 ≦ x <1) between the ScAlMgO ₄ substrate 001 and the GaN crystal 004, as shown in FIG. May be. FIG. 2 is a schematic cross-sectional view of a group III nitride semiconductor 101 according to a modification.

The Al _x Ga _1-x N layer 007 can be formed by the following method, for example. Here, the film thickness of the Al _x Ga _1-x N layer 007 is 2 μm. The composition x of Al is 0.02 (2 atm%).

First, a ScAlMgO ₄ substrate 001 as a seed substrate is prepared. After the prepared substrate is thermally cleaned in a hydrogen atmosphere at about 1000 ° C., a buffer layer is formed at a low temperature of about 600 ° C. and a thickness of about 20 to 50 nm. Then, an Al _x Ga _1-x N layer 007 is grown at 1050 ° C. by MOCVD. By forming the buffer layer, higher quality crystals can be obtained. The composition of the buffer layer is preferably the same as that of the Al _x Ga _1-x N layer 007.

If the Al composition of the Al _x Ga _1-x N layer 007 is 2 atm% or more and 10 atm% or less, there is no problem because the lattice constant does not dissociate excessively from GaN. After the Al _x Ga _1-x N layer 007 is formed, the mask layer 002 described in the above embodiment is formed. In the modification, the mask layer 002 is formed to have the stripe-shaped opening 008. However, the shape of the opening 008 of the mask layer 002 is not limited to the shape. Here, in the above-described embodiment, the ScAlMgO ₄ substrate 001 is directly exposed in the opening 008 of the mask layer 002, whereas in the modification, the Al _x Ga _1-x N layer 007 is formed in the opening 008 of the mask layer 002. Exposed. In this modification, the GaN crystal 004 is grown using the exposed Al _x Ga _1-x N layer 007 as a starting point.

Also in the modification, defects 313 are generated in the Al _x Ga _1-x N layer 007 and the GaN crystal 004 formed in the vicinity of the plurality of openings 008, but these concentrate only in the vicinity of the opening 008 of the mask layer 002. Defects do not propagate to most regions of the GaN crystal 004. Therefore, the GaN crystal 004 formed on the convex part 009 of the mask layer 002 exhibits high crystallinity.

Here, if there are many lattice mismatches and thermal expansion mismatches between the seed substrate (ScAlMgO ₄ substrate 001) and the GaN crystal 004 to be grown, the grown GaN crystal 004 warps due to the influence of the residual stress, and the bonding portion When bonding is performed at 316, bonding may not be performed smoothly at the atomic layer level, and a new defect may occur in this region. The new defects are scattered around the periphery as the GaN grows further, and eventually causes an increase in the dislocation density of the entire GaN crystal 004. On the other hand, by providing the Al _x Ga _1-x N layer 007 as in the modification example, the influence of lattice mismatch and thermal expansion mismatch can be reduced. Accordingly, a region 318 with fewer defects can be formed on substantially the entire surface excluding the region 317 with many defects. The dislocation density in the region 318 with few defects can be less than 1 × 10 ⁶ m ⁻² .

Also in the modified example, the effect of increasing the lattice constant by diffusing Mg from the ScAlMgO ₄ substrate 001 into the Al _x Ga _1-x N layer 007 and the GaN crystal 004 is the same as in the above-described embodiment. That is, Mg atoms diffuse from the ScAlMgO ₄ substrate 001 to the GaN crystal 004 side in the region 319 near the opening 008 of the mask layer 002. As a result, warpage of the GaN crystal 004 is reduced, and a high-quality GaN crystal 004 is obtained.

Note that instead of the Al _x Ga _1-x N layer 007, a layer made of an Al _x Ga _y In _1-xy N (0 ≦ x <1, x + y = 1) mixed crystal to which In is added is used. Is also possible.

(Other)
The group III nitride semiconductor of this indication can be used for various uses. For example, the group III nitride semiconductor of the present disclosure can be used for substrates of various light emitting devices. In this case, an AlGaInN-based crystal that is a light-emitting diode having a wavelength range of ultraviolet to red or a light-emitting layer of a laser diode is grown on the group III nitride crystal by the MOCVD method or the like. By forming such a light emitting layer using the group III nitride semiconductor of the present disclosure, the defect density of the light emitting layer is lowered. As a result, it is possible to significantly improve the light emission efficiency and the operating life of the light emitting element.

Further, in the above-described embodiment, it has been described that the GaN crystal is manufactured by the MOCVD method. A GaN crystal may be produced by the method described above. In both the HVPE method and the OVPE method, the substrate temperature during crystal growth is about 1000 ° C. or more as in the MOCVD method, and Mg atoms diffuse from the ScAlMgO ₄ substrate. Further, after forming a GaN layer of several hundred microns to several mm by HVPE method or OVPE method on the GaN crystal of group III nitride semiconductor produced by the MOCVD method, the ScAlMgO ₄ substrate is polished. A GaN self-supporting substrate may be fabricated by removing using a technique.

In the above description, an example in which a GaN crystal is formed as a group III nitride crystal has been described. However, the group III nitride crystal formed in the present embodiment is not limited to a GaN crystal. For example, Al _x Ga _1-x N (0 ≦ x ≦ 1) may be formed at a high temperature of about 900 to 1000 ° C. by the same method as described above. However, when the Al composition is increased, AlN polycrystals are deposited on the mask layer 002, and the selective growth of crystals is reduced. Therefore, the concentration of Al contained in the crystal is preferably more than 0 atm% and not more than 10 atm%, more preferably more than 0 atm% and not more than 5 atm%.

In addition, after producing a GaN crystal by the above-mentioned method, a ScAlMgO ₄ substrate (RAMO ₄ substrate) and a different kind of film may be removed, and a group III nitride crystal may be taken out and used as a group III nitride semiconductor. The removal of the ScAlMgO ₄ substrate (RAMO ₄ substrate) and the dissimilar film is performed by processing such as grinding or polishing.

Here, when the group III nitride semiconductor is manufactured by the method of the present disclosure, the group is selected from the group consisting of Mg, Mn, Fe (II), Co, Cu, Zn, and Cd in the same plane constituting the crystal. A group III nitride semiconductor having a group III nitride crystal in which a region containing one or a plurality of divalent elements and a region not containing the divalent element are alternately distributed is obtained. Since the group III nitride semiconductor includes a region containing the above divalent element, the mismatch of the lattice constant between the RAMO ₄ substrate and the group III nitride crystal that occurs during the production of the group III nitride crystal is improved. It becomes a high-quality group III nitride semiconductor. Note that the concentration of the divalent element in the region containing the divalent element is preferably 7 × 10 ^{17 to} 5 × 10 ²¹ [atoms / cm ³ ], and preferably 1 × 10 ^{20 to} 5 × 10. ²¹ [atoms / cm ³ ] is more preferable. By containing a divalent element having a concentration in this range, a high-quality group III nitride semiconductor is obtained. In addition, as described above, when ScAlMgO ₄ is used as a substrate for producing the group III nitride semiconductor, the divalent element described above is Mg. The group III nitride crystal in such a group III nitride semiconductor is preferably a GaN crystal.

  The group III nitride semiconductor of the present disclosure can be used as a seed substrate for crystal growth of white LEDs and semiconductor laser diodes used for lighting, automobile headlights, and the like.

001 ScAlMgO ₄ substrate (RAMO ₄ substrate)
002 Mask layer (dissimilar film)
003 Resist film 004 GaN crystal (Group III nitride crystal)
006 Bonding portion 007 Al _x Ga _1-x N layer 008 Opening 009 Protruding portion 313 Defect 316 Bonding portion 317 High defect region 318 Low defect region 319, 320 Region where Mg diffuses

Claims (17)

A single crystal represented by the general formula RAMO ₄ (in the general formula, R represents one or more trivalent elements selected from the group consisting of Sc, In, Y, and lanthanoid elements; Represents one or more trivalent elements selected from the group consisting of Fe, (III), Ga, and Al, and M represents Mg, Mn, Fe (II), Co, Cu, Zn, and Cd. A RAMO ₄ substrate comprising one or more divalent elements selected from the group consisting of:
The RAMO ₄ is formed on a substrate, formed of a material different from the RAMO ₄ substrate, and a heterogeneous membrane having a plurality of openings,
A group III nitride crystal formed on the heterogeneous film and in the opening of the heterogeneous film, made of a material different from the heterogeneous film, and containing an element represented by M in the general formula;
A group III nitride semiconductor having: The concentration of the element represented by M in the opening of the heterogeneous film of the group III nitride crystal is 7 × 10 ^{17 to} 5 × 10 ²¹ [atoms / cm ³ ]. Group III nitride semiconductor. 2. The concentration of the element represented by M in the opening of the heterogeneous film of the group III nitride crystal is 1 × 10 ^{20 to} 5 × 10 ²¹ [atoms / cm ³ ]. Group III nitride semiconductor. The group III nitride semiconductor according to any one of claims 1 to 3, wherein the heterogeneous film is in direct contact with the RAMO ₄ substrate.   The group III nitride semiconductor according to claim 1, wherein the different type film is a dielectric or a metal. The group III nitride semiconductor according to claim 1, wherein the group III nitride crystal is in direct contact with the RAMO ₄ substrate through the plurality of openings.   The group III nitride semiconductor according to claim 1, wherein R in the general formula is Sc, A is Al, and M is Mg. A region containing one or more divalent elements selected from the group consisting of Mg, Mn, Fe (II), Co, Cu, Zn, and Cd in the same plane constituting the crystal; a region containing no valence elements, but the group III nitride crystal distributed alternately possess,
The group III nitride semiconductor , wherein the region containing the divalent element has more threading dislocations than the region not containing the divalent element . The group III nitride semiconductor according to claim 8, wherein in the region containing the divalent element, the concentration of the divalent element is 7 × 10 ^{17 to} 5 × 10 ²¹ [atoms / cm ³ ]. The group III nitride semiconductor according to claim 8, wherein in the region containing the divalent element, the concentration of the divalent element is 1 × 10 ^{20 to} 5 × 10 ²¹ [atoms / cm ³ ].   The group III nitride semiconductor according to claim 1, wherein the group III nitride crystal is GaN. A single crystal represented by the general formula RAMO ₄ (in the general formula, R represents one or more trivalent elements selected from the group consisting of Sc, In, Y, and lanthanoid elements; Represents one or more trivalent elements selected from the group consisting of Fe, (III), Ga, and Al, and M represents Mg, Mn, Fe (II), Co, Cu, Zn, and Cd. Preparing a RAMO ₄ substrate comprising one or more divalent elements selected from the group consisting of:
The RAMO ₄ on the substrate and forming the RAMO ₄ consists substrate of a material different, and different films including a plurality of openings,
Forming a group III nitride crystal made of a material different from the different film on the different film at 900 to 1000 ° C .;
A method for producing a group III nitride semiconductor comprising: The method for producing a group III nitride semiconductor according to claim 12, wherein the heterogeneous film is formed so as to be in direct contact with the RAMO ₄ substrate.   The method of manufacturing a group III nitride semiconductor according to claim 12 or 13, wherein the dissimilar film is made of a dielectric or a metal. The method for producing a group III nitride semiconductor according to any one of claims 12 to 14, wherein the group III nitride crystal is formed so as to be in direct contact with the RAMO ₄ substrate through the plurality of openings. .   In the said general formula, R is Sc, A is Al, M is Mg, The manufacturing method of the group III nitride semiconductor as described in any one of Claims 12-15. The method for producing a group III nitride semiconductor according to any one of claims 12 to 16, wherein the group III nitride crystal is GaN.