JP2005229134A - Forming method of nitride semiconductor layer, nitride semiconductor, manufacturing method of the nitride semiconductor element, and the nitride semiconductor element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a forming method of a nitride semiconductor layer, a forming method of a nitride semiconductor element, a nitride semiconductor, and a nitride semiconductor element, by which appropriate orientation can be selected from a plurality of crystal orientations and an element region can be arranged. <P>SOLUTION: On the surface of a GaN layer 3, provided on a sapphire substrate, a plurality of scattered hexagonal patterns 5 are formed. A regrowth GaN layer 6 is epitaxially grown, according to lateral growth method, from the surface of the GaN layer 3 exposed among the hexagonal patterns 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a group III-V nitride semiconductor such as BN (boron nitride), GaN (gallium nitride), AlN (aluminum nitride), InN (indium nitride), TlN (thallium nitride), or a mixed crystal thereof (hereinafter referred to as a group III-V nitride semiconductor). The present invention relates to a method for forming a nitride-based semiconductor layer made of a nitride-based semiconductor, a nitride-based semiconductor, a method for manufacturing a nitride-based semiconductor element, and a nitride-based semiconductor element.

In recent years, GaN-based semiconductor light-emitting elements have been put into practical use as semiconductor light-emitting elements such as light-emitting diodes and semiconductor laser elements that generate blue or violet light. At the time of manufacturing a GaN-based semiconductor light-emitting element, since a substrate made of GaN does not exist, a GaN layer is epitaxially grown on an insulating substrate such as sapphire (Al ₂ O ₃ ).

However, in the GaN-based semiconductor light-emitting device, there are about 10 ¹¹ to 10 ¹² lattice defects / cm ⁻² in the GaN crystal grown on the sapphire substrate due to the difference in lattice constant between the GaN and sapphire substrates. Among such lattice defects, there are many lattice defects (hereinafter referred to as threading dislocations) penetrating the GaN layer grown on the sapphire substrate. In a semiconductor light emitting device composed of a GaN layer on a sapphire substrate, this threading dislocation causes leakage current and impurity diffusion in the semiconductor light emitting device, resulting in deterioration of device characteristics and reliability. As a method for solving the problem of deterioration in device characteristics and reliability due to threading dislocations, a lateral growth method in which a semiconductor layer is grown in a lateral direction has been proposed.

  FIG. 17A is a plan view showing a GaN layer formed by a later-described conventional lateral growth method, and FIG. 17B is a cross-sectional view taken along the line AA in FIG.

In order to obtain the structure shown in FIG. 17, first, an undoped AlGaN buffer layer 42 and an undoped GaN layer 43 are successively grown on the sapphire substrate 41 in order. The GaN layer 43 has threading dislocations extending in the vertical direction. A striped SiO ₂ film 44 is formed on the GaN layer 43.

Next, an undoped GaN layer 46 is regrown on the striped SiO ₂ film 44 and the GaN layer 43 by the HVPE (Hydride Vapor Phase Epitaxy) method. At this time, since on the SiO ₂ do not grow crystals, on the SiO ₂ film 44 GaN layer 46 is formed by the lateral growth. Thereby, the defect density of the GaN layer 46 is reduced to about 6 × 10 ⁷ cm ⁻² .

In the above lateral growth method, the growth in the lateral direction toward the center portion of the SiO ₂ film 44 advances from the GaN layer 43 exposed between the SiO ₂ film 44, a region 45 of the central portion of the SiO ₂ film 44 Threading dislocations are concentrated.

  FIG. 18 is a diagram for explaining another example of a conventional lateral growth method. 18A and 18B are schematic process cross-sectional views showing the formation of a GaN layer by a lateral growth method, and FIG. 18C is a top view of the structure shown in FIG. 18B.

In order to obtain the structure shown in FIG. 18A, first, a GaN layer 51 of 2 to 4 μm is formed on the sapphire substrate 50. A striped SiO ₂ mask is formed on the GaN layer 51, and the GaN in the opening of the SiO ₂ mask is etched to the sapphire substrate 50 by dry etching. Further, the SiO ₂ mask on the GaN layer 51 remaining without being etched is removed. Thereby, a striped GaN layer 51 is formed on the sapphire substrate 50 as shown in FIG.

  Next, GaN is grown again from the striped GaN layer 51. At this time, the growth rate of GaN growing from the side surface direction of the striped GaN layer 51 exceeds the growth rate of GaN growing from the upper surface of the GaN layer 51, and the GaN grown from the side surface direction is connected with the passage of time. Thus, a mirror-flat GaN layer 53 as shown in FIG. 18B is formed. As shown in FIG. 18B, threading dislocations 52 that reach the sapphire substrate 50 are formed on the striped GaN layer 51 of FIG. The threading dislocations 52 are distributed in the region 55 on the GaN layer 51 as shown in FIG.

In the method of forming a nitride-based semiconductor layer using the lateral growth method as described above, threading dislocations are formed in the regions 45 and 55 extending linearly along the SiO ₂ film 44 or the GaN layer 51 extending in a stripe shape. Many 52 occur.

When a semiconductor laser element is formed on such GaN layers 46 and 53, the resonator must be formed along the striped SiO ₂ film 44 or GaN layer 51, and the semiconductor laser in the GaN layers 46 and 53 is formed. The degree of freedom of element arrangement is limited to one direction.

  An object of the present invention is to provide a nitride-based semiconductor layer forming method, a nitride-based semiconductor device manufacturing method, and a nitride-based semiconductor device capable of arranging an element region by selecting an appropriate orientation from a plurality of crystal orientations. It is to provide a semiconductor and a nitride semiconductor device.

Means for Solving the Problems and Effects of the Invention

  According to a first aspect of the present invention, there is provided a method for forming a nitride-based semiconductor layer, comprising: forming a concavo-convex pattern composed of a plurality of convex portions scattered in an island shape on a surface of a base composed of a first nitride-based semiconductor layer or a substrate. The second nitride semiconductor layer is formed on the concavo-convex pattern.

  In the method for forming a nitride-based semiconductor layer according to the present invention, a second nitride-based semiconductor layer is formed by lateral growth and vertical growth on a concavo-convex pattern composed of a plurality of convex portions scattered in an island shape. The In this case, threading dislocations are concentrated on a plurality of convex portions scattered in an island shape. Thereby, the parts where threading dislocations are concentrated are discretely arranged without being continuous.

  Therefore, it is possible to select any continuous region among the regions between the convex portions, and to form the element region above the selected region. As a result, an appropriate orientation can be selected from a plurality of crystal orientations to form a high-quality element region.

  A concavo-convex pattern may be formed on the surface of the base by forming a plurality of crystal growth blocking layers on the base made of the first nitride-based semiconductor layer as the plurality of convex portions.

  In this case, threading dislocations concentrate at the center of each second nitride semiconductor layer grown on each crystal growth blocking layer. Thereby, threading dislocations are discretely arranged. Therefore, the element region can be arranged by selecting any continuous direction without threading dislocations.

  An uneven pattern may be formed on the surface of the base by forming a plurality of nitride-based semiconductor layers on the base made of the first nitride-based semiconductor layer or the substrate as the plurality of convex portions.

  In this case, threading dislocations concentrate on each nitride-based semiconductor layer. Thereby, threading dislocations are discretely arranged. Therefore, the element region can be arranged by selecting any continuous direction without threading dislocations.

  A plurality of crystal growth inhibition layers are formed on a base made of a first nitride semiconductor layer stacked on a substrate as a plurality of protrusions, and the first nitride semiconductor is formed using the plurality of crystal growth inhibition layers as a mask. An uneven pattern may be formed on the underlying surface by etching the layer.

  In this case, threading dislocations concentrate at the center of each second nitride semiconductor layer grown on each crystal growth blocking layer. Thereby, threading dislocations are discretely arranged. Therefore, an element region can be arranged by selecting an arbitrary direction in which threading dislocations are continuous.

  The plurality of convex portions may be circular or polygonal. In this case, the hexagonal second nitride-based semiconductor layer grows almost naturally on the circular or polygonal convex portion, so that the defect density of the second nitride-based semiconductor layer is reduced.

  The polygon is preferably a hexagon. In this case, since the hexagonal second nitride semiconductor layer grows naturally on the hexagonal convex portion, the defect density of the second nitride semiconductor layer is further reduced.

  The plurality of convex portions and the second nitride-based semiconductor layer on each convex portion may be removed, and a third nitride-based semiconductor layer may be formed in the removed region.

  In this case, after each second nitride-based semiconductor layer having threading dislocations on each convex portion is removed, a third nitride-based semiconductor layer is formed between the remaining second nitride-based semiconductor layers. Therefore, the defect density of the second nitride semiconductor layer and the third nitride semiconductor layer formed on the concave / convex pattern is sufficiently reduced.

  In the nitride semiconductor according to the second invention, a concavo-convex pattern consisting of a plurality of convex portions scattered in an island shape is formed on the surface of the base made of the first nitride semiconductor layer or substrate, The second nitride-based semiconductor layer is formed.

  In the nitride-based semiconductor according to the present invention, the second nitride-based semiconductor layer is formed by lateral growth and vertical growth on the concavo-convex pattern composed of a plurality of convex portions scattered in an island shape. In this case, threading dislocations are concentrated on a plurality of convex portions scattered in an island shape. Thereby, the parts where threading dislocations are concentrated are discretely arranged without being continuous.

  Therefore, it is possible to select any continuous region among the regions between the convex portions, and to form the element region above the selected region. As a result, an appropriate orientation can be selected from a plurality of crystal orientations to form a high-quality element region.

  The plurality of convex portions may be a plurality of crystal growth inhibition layers formed on a base made of the first nitride-based semiconductor layer.

  In this case, threading dislocations concentrate at the center of each second nitride semiconductor layer grown on each crystal growth blocking layer. Thereby, threading dislocations are discretely arranged. Therefore, the element region can be arranged by selecting any continuous direction without threading dislocations.

  The plurality of protrusions may be a first nitride-based semiconductor layer or a plurality of nitride-based semiconductor layers formed on a base made of a substrate.

  In this case, threading dislocations concentrate on each nitride-based semiconductor layer. Thereby, threading dislocations are discretely arranged. Therefore, the element region can be arranged by selecting any continuous direction without threading dislocations.

  The plurality of protrusions may be a first nitride semiconductor layer or a plurality of nitride semiconductor layers and a crystal growth blocking layer stacked on a base made of a substrate.

  In this case, threading dislocations concentrate at the center of each second nitride semiconductor layer grown on each crystal growth blocking layer. Thereby, threading dislocations are discretely arranged. Therefore, an element region can be arranged by selecting an arbitrary direction in which threading dislocations are continuous.

  According to a third aspect of the present invention, there is provided a method for manufacturing a nitride-based semiconductor device, comprising: forming a concavo-convex pattern including a plurality of convex portions scattered in an island shape on a surface of a base formed of a first nitride-based semiconductor layer or a substrate. A second nitride-based semiconductor layer is formed on the concave / convex pattern, and a third nitride-based semiconductor layer including an element region is formed on the second nitride-based semiconductor layer.

  In the method for manufacturing a nitride-based semiconductor device according to the present invention, the second nitride-based semiconductor layer is formed by lateral growth and vertical growth on the concavo-convex pattern including a plurality of convex portions scattered in an island shape. The In this case, threading dislocations are concentrated on a plurality of convex portions scattered in an island shape. Thereby, the parts where threading dislocations are concentrated are discretely arranged without being continuous.

  Therefore, an arbitrary continuous region among the regions between the convex portions can be selected, and the element region in the third nitride-based semiconductor layer can be formed above the selected region. As a result, an appropriate orientation can be selected from a plurality of crystal orientations to form a high-quality element region.

  A plurality of convex portions may be two-dimensionally arranged along a plurality of directions, and a light emitting region extending along any one of the plurality of directions may be formed in an upper element region between the plurality of convex portions.

  In this case, since the defect density of the second nitride-based semiconductor layer in the upper part between the plurality of convex portions is low, a region having a low defect density continues to the second nitride-based semiconductor layer in a plurality of directions. Therefore, an arbitrary direction can be selected from a plurality of directions, and a high-quality light emitting region can be formed along the selected region.

  According to a fourth aspect of the present invention, there is provided a nitride semiconductor device, wherein a concave / convex pattern including a plurality of convex portions scattered in an island shape is formed on a surface of a base made of a first nitride semiconductor layer or a substrate. A second nitride semiconductor layer is formed thereon, and a third nitride semiconductor layer including an element region is formed on the second nitride semiconductor layer.

  In the nitride semiconductor device according to the present invention, the second nitride semiconductor layer is formed by lateral growth and vertical growth on the concavo-convex pattern composed of a plurality of convex portions scattered in islands. In this case, threading dislocations are concentrated on a plurality of convex portions scattered in an island shape. Thereby, the parts where threading dislocations are concentrated are discretely arranged without being continuous.

  Therefore, an arbitrary continuous region among the regions between the convex portions can be selected, and the element region in the third nitride-based semiconductor layer can be formed above the selected region. As a result, an appropriate orientation can be selected from a plurality of crystal orientations to form a high-quality element region.

  The plurality of convex portions may be two-dimensionally arranged along a plurality of directions, and the element region may include a light emitting region extending along any one of the plurality of directions in the upper element region between the plurality of convex portions. .

  In this case, since the defect density of the second nitride-based semiconductor layer in the upper part between the plurality of convex portions is low, a region having a low defect density continues to the second nitride-based semiconductor layer in a plurality of directions. Therefore, an arbitrary direction can be selected from a plurality of directions, and a high-quality light emitting region can be formed along the selected region.

  The light emitting region may constitute a resonator. In this case, a high quality resonator can be formed by selecting an arbitrary direction from a plurality of directions.

  FIG. 1 is a schematic process sectional view showing a method of forming a GaN-based semiconductor layer in the first embodiment of the present invention.

First, as shown in FIG. 1A, a buffer layer 2 made of undoped Al _0.5 Ga _0.5 N and having a thickness of about 200 μm and an undoped GaN layer 3 having a thickness of about 3 μm are sequentially formed on the C surface of the sapphire substrate 1. Grow. The buffer layer 2 is grown at a substrate temperature of 600 ° C., and the GaN layer 3 is grown at 1080 ° C. by MOCVD (metal organic chemical vapor deposition).

Next, as shown in FIG. 1B, a SiO ₂ film 4 of about 1 μm is formed on the GaN layer 3 by plasma CVD (chemical vapor deposition).

As shown in FIG. 1C, photolithography and etching with a hydrofluoric acid-based etchant are performed to form a plurality of hexagonal patterns 5 made of SiO ₂ . The length W ₁ of the diagonal line of this pattern 5 is 15 μm, and the pitch W ₂ of the adjacent pattern 5 is 20 μm.

  Subsequently, as shown in FIG. 1 (d), an undoped regrown GaN layer 6 is regrown at a substrate temperature of 1080 ° C. on the GaN layer 3 exposed between the hexagonal patterns 5.

  Thereafter, an element region of a semiconductor laser element made of a nitride semiconductor layer is formed on the regrown GaN layer 6.

2 and 3 are plan views showing examples of a two-dimensional array of hexagonal patterns 5. In the example of FIG. 2, the plurality of hexagonal patterns 5 are two-dimensionally arranged along the α direction and the β direction that are orthogonal to each other. That is, the patterns 5 are arranged at the minimum pitch W ₂ in two directions, the α direction and the β direction. In FIG. 2, the α direction is parallel to one of the diagonal lines of the hexagonal pattern 5.

On the other hand, in the example of FIG. 3, the plurality of hexagonal patterns 5 are two-dimensionally arranged along the φ direction, the γ direction, and the θ direction that form an angle of 60 ° with each other. That is, the patterns 5 are arranged at the minimum pitch W ₂ in the φ direction, the γ direction, and the θ direction. In this case, the φ direction, the γ direction, and the θ direction are parallel to any one of the diagonal lines of the hexagonal pattern 5.

  When the pattern 5 is arranged as shown in FIG. 2, the α direction of the arrangement of the pattern 5 and the <11-20> direction of the GaN layer 3 are matched. Further, when arranged in this way, two hexagonal sides of the pattern 5 are perpendicular to the <10-10> direction of the GaN layer 3. In this case, the light emitting region of the resonator of the semiconductor laser element can be arranged along either the α direction or the β direction. When the resonator end face is formed, if the resonator length direction is arranged in the α direction, it can be cleaved in the {11-20} plane, and if arranged in the β direction, it is cleaved in the {10-10} plane. be able to.

  When the pattern 5 is arranged as shown in FIG. 3, the φ direction of the arrangement of the pattern 5 and the <11-20> direction of the GaN layer 3 are matched. In this case, the light emitting region of the resonator of the semiconductor laser element can be arranged along any one of the φ direction, the γ direction, and the θ direction. When the resonator end face is formed, cleavage can be performed at {11-20} if the resonator length direction is arranged in the φ direction, the γ direction, or the θ direction.

Further, by arranging as described above, the plane orientation of the regrowth GaN layer 6 and the side plane orientation of the hexagonal pattern 5 coincide with each other, so that the crystal distortion hardly occurs like the natural growth of GaN, The defect density is as low as 10 × 10 ⁷ cm ⁻² or less.

  4A is a plan view showing the distribution of threading dislocations in the formation direction of the GaN-based semiconductor layer of FIG. 1, and FIG. 4B is a cross-sectional view taken along line A1-A1 of FIG.

  In the regrown GaN layer 6 of the present embodiment, threading dislocations 7 are concentrated in the region on the center of the pattern 5 as shown in FIG. For this reason, a region with few threading dislocations 7 is widened, and the distribution of threading dislocations 7 is not continuous but discrete. As shown in FIG. 2 or FIG. 3, if the patterns 5 are arranged in the form of islands, the concentrated regions of threading dislocations 7 can be scattered in the regrowth GaN layer 6. Thereby, while avoiding the region where the threading dislocations 7 are concentrated, the light emitting region of the elongated resonator of 200 μm or more can be arranged by selecting any one direction from a plurality of directions.

It may form a circular pattern of SiO ₂ instead of hexagonal pattern 5 made of SiO ₂ in FIG.

5 and 6 are plan views showing examples of a two-dimensional array of circular patterns. In the example of FIG. 5, a plurality of circular patterns 5 </ b> A are two-dimensionally arranged along the orthogonal α direction and β direction, similarly to the two-dimensional array of patterns 5 shown in FIG. 2. The diameter W ₅ pattern 5A in FIG. 5 is 15μm for example, the pitch W ₆ being a 20 [mu] m. When the pattern 5A is two-dimensionally arranged as shown in FIG. 5, the α direction of the array of the circular patterns 5A and the <11-20> direction of the GaN layer 3 are matched. Alternatively, the α direction of the arrangement of the pattern 5A and the <10-10> direction of the GaN layer 3 are matched.

  In this case, the light emitting region of the resonator of the semiconductor laser element can be arranged along either the α direction or the β direction. When the resonator end face is formed, if the α direction and the <11-20> direction of the GaN layer 3 are made coincident and the direction of the resonator length is arranged in the α direction, it can be cleaved at the {11-20} plane, and β If it is arranged in the direction, it can be cleaved at the {10-10} plane, and if the direction of the resonator length is arranged in the α direction with the β direction and the <10-10> direction of the GaN layer 3 matched, {11-20 } Can be cleaved on the plane, and can be cleaved on the {10-10} plane if arranged in the β direction.

On the other hand, in the example of FIG. 6, a plurality of circular patterns 5A are two-dimensionally arranged along the φ direction, the γ direction, and the θ direction that form an angle of 60 ° with each other. The diameter W ₅ of the pattern 5A in FIG. 6 is, for example, 15 μm, and the pitch W ₆ is 20 μm. When the pattern 5A is two-dimensionally arranged as shown in FIG. 5, the arrangement of the circular pattern 5A is made to coincide with the φ direction and the <11-20> direction of the GaN layer 3. Alternatively, the φ direction of the arrangement of the patterns 5A and the <10−10> direction of the GaN layer 3 are matched. In this case, the light emitting region of the resonator of the semiconductor laser element can be arranged along any one of the φ direction, the γ direction, and the θ direction. When forming the cavity end face, if the φ direction, γ direction, or θ direction and the <11-20> direction of the GaN layer 3 are matched, the direction of the resonator length is arranged in the φ direction, γ direction, or θ direction. , {11-20} plane. If the direction of the resonator length is arranged in the φ direction, the γ direction, or the θ direction by making the φ direction, the γ direction, or the θ direction coincide with the <10-10> direction of the GaN layer 3, {10-10} Can be cleaved on the surface.

  7A is a plan view showing the distribution of threading dislocations when the pattern 5A is two-dimensionally arranged as shown in FIG. 6, and FIG. 7B is a cross-sectional view taken along line A2-A2 of FIG. is there. As shown in FIG. 7, since the threading dislocations 7 are concentrated on the regrowth GaN layer 6 on the center of the pattern 5A, the region with few threading dislocations 7 is expanded.

  FIG. 8 is a schematic process cross-sectional view showing a method for forming a GaN-based semiconductor layer in the second embodiment of the present invention. First, in the step shown in FIG. 8A, a buffer layer 2 having a thickness of 200 mm and a GaN layer 3 having a thickness of about 3 μm are formed in order as in the step shown in FIG.

Next, as shown in FIG. 8B, a SiO ₂ film 4 of about 1 μm is formed on the GaN layer 3 by MOCVD (metal organic chemical vapor deposition).

As shown in FIG. 8C, photolithography and etching with a hydrofluoric acid-based etchant are performed to form a plurality of circular patterns 5A made of SiO ₂ . The plurality of circular patterns 5A are arranged as shown in FIG.

  The exposed GaN layer 3 is etched by plasma etching or the like using the plurality of circular patterns 5A as a mask. Thereby, as shown in FIG. 8D, a plurality of GaN layers 8A scattered in an island shape are formed.

Next, as shown in FIG. 8E, the pattern 5A made of the SiO ₂ film is removed with hydrofluoric acid or the like.

  Next, using the lateral growth method, the regrowth GaN layer 9 is regrown by about 20 μm by MOCVD or HVPE at a substrate temperature of 1080 ° C. as shown in FIG. Thereby, the regrowth GaN layer 9 is formed in a mirror-flat surface.

  Thereafter, an element region of a semiconductor laser element made of a nitride semiconductor layer is formed on the regrown GaN layer 9.

  FIG. 9A is a plan view showing the distribution of threading dislocations in the method for forming the GaN-based semiconductor layer of FIG. 8, and FIG. 9B is a cross-sectional view taken along line A3-A3 of FIG.

  In the regrown GaN layer 9 of the present embodiment, threading dislocations 10 extend to the regrown GaN layer 9 on the circular GaN layer 8A formed before the growth of the regrown GaN layer 9 as shown in FIG. ing. For this reason, the distribution of threading dislocations 10 is not continuous but discrete. As shown in FIG. 5 or FIG. 6, if the patterns 5 </ b> A are scattered in an island shape, even in the regrown GaN layer 9, regions with many threading dislocations 10 can be scattered. Thereby, while avoiding a region where there are many threading dislocations 10, a light emitting region of an elongated resonator having a size of 200 μm or more can be arranged by selecting one of a plurality of directions.

Instead of the circular pattern 5A made of SiO ₂ in FIG. 8, a hexagonal pattern 5 made of SiO ₂ shown in FIG. 2 or FIG. 3 may be formed. In this case, the threading dislocation distribution is as shown in FIG. FIG. 10A is a plan view showing the distribution of threading dislocations in the method for forming the GaN-based semiconductor layer of FIG. 8, and FIG. 10B is a cross-sectional view taken along line A4-A4 of FIG.

  In the second embodiment, the etching is performed so as to leave the buffer layer 2 as shown in FIG. 8D. However, in the process of FIG. 8D, the pattern 5A is used as a mask until the sapphire substrate 1 is reached. Etching may be performed.

  FIG. 11 is a schematic process sectional view showing a method of forming a GaN-based semiconductor layer in the third embodiment of the present invention.

  First, in the step shown in FIG. 11A, a 200-inch buffer layer 2 and a GaN layer 3 having a thickness of about 2 μm are sequentially formed in the same manner as in the step shown in FIG.

Next, as shown in FIG. 11B, an SiO ₂ film 4 of about 1 μm is formed on the GaN layer 3 by MOCVD.

As shown in FIG. 11C, photolithography and etching with a hydrofluoric acid-based etching solution are performed to form a plurality of circular patterns 5A made of a SiO ₂ film. The plurality of circular patterns 5A are arranged as shown in FIG.

  The exposed GaN layer 3 is etched by plasma etching or the like using the plurality of circular patterns 5A as a mask. Thereby, as shown in FIG. 11D, a plurality of GaN layers 8A scattered in an island shape are formed.

  Next, using the lateral growth method, the regrowth GaN layer 9A is regrown by about 20 μm as shown in FIG. 11E by MOCVD method or HVPE method at a substrate temperature of 1080 ° C. As a result, the regrowth GaN layer 9A is formed to be mirror-flat.

  Thereafter, an element region of a semiconductor laser element made of a nitride semiconductor layer is formed on the regrown GaN layer 9A.

  The regrowth GaN layer 9A formed as shown in FIG. 11 can also be applied to a semiconductor laser device in the same manner as the regrowth GaN layer 9 shown in FIG.

  12A is a plan view showing the distribution of threading dislocations in the method for forming the GaN-based semiconductor layer of FIG. 11, and FIG. 12B is a cross-sectional view taken along line A5-A5 of FIG.

  In the regrown GaN layer 9A of the present embodiment, threading dislocations 11 extend to the central region of the circular pattern 5A formed before the regrown GaN layer 9A is grown as shown in FIG. For this reason, a region having few threading dislocations 11 is widened, and the distribution of threading dislocations 11 is not continuous but discrete. If the pattern 5A is scattered in an island shape, a light emitting region of a 200 μm or more long resonator is selected from a plurality of directions while avoiding a region where threading dislocations 11 are concentrated. Can do.

Instead of the circular pattern 5A made of SiO ₂ in FIG. 11, a hexagonal pattern 5 made of SiO ₂ shown in FIG. 2 or FIG. 3 may be formed. In this case, the threading dislocation distribution is as shown in FIG. FIG. 13A is a plan view showing the distribution of threading dislocations in the method for forming the GaN-based semiconductor layer of FIG. 11, and FIG. 13B is a cross-sectional view taken along line A6-A6 of FIG.

  In the third embodiment, etching is performed so as to leave the buffer layer 2 as shown in FIG. 11D. However, in the process of FIG. 11D, the pattern 5A is used as a mask until the sapphire substrate 1 is reached. Etching may be performed.

  FIG. 14 is a schematic process cross-sectional view showing a method of forming a GaN-based semiconductor layer in the fourth embodiment of the present invention.

  First, by the manufacturing process of the second embodiment, a structure in which the buffer layer 2 is formed on the sapphire substrate 1 and the regrowth GaN layer 9 is formed on the buffer layer 2 as shown in FIG. That is, the structure shown in FIG.

Next, an SiO ₂ film of about 1 μm is formed on the regrown GaN layer 9 by plasma CVD or the like. Then, as shown in FIG. 14B, the SiO ₂ film on the region excluding the region where the GaN layer 8A was originally formed is removed to form a pattern 12 made of SiO ₂ .

  Next, etching is performed using the pattern 12 of FIG. 14B as a mask to remove the region where the threading dislocations 10 are formed. As a result, as shown in FIG. 14C, the GaN layer 13 not including the threading dislocation 10 is formed on the buffer layer 2.

  Next, using the lateral growth method, the regrown GaN layer 14 is regrown by about 20 μm as shown in FIG. 14D by MOCVD method or HVPE method at a substrate temperature of 1080 ° C. Thereby, the regrowth GaN layer 14 is formed to be mirror-flat.

  Thereafter, an element region of a semiconductor laser element made of a nitride semiconductor layer is formed on the regrown GaN layer 14.

  Note that the region to be removed by etching may partially overlap with the region where the GaN layer 8A has been formed as shown in FIG.

  In the fourth embodiment, etching is performed so as to leave the buffer layer 2 as shown in FIG. 14C. However, in the process of FIG. 14C, etching is performed until the sapphire substrate 1 is reached. Good.

  In the GaN layer 14 of the present embodiment, the threading dislocations 10 are extremely small. For example, the position where the resonator of the semiconductor laser device is disposed is not restricted by the distribution of the threading dislocations 10.

  FIG. 16 is a schematic sectional view of a GaN-based semiconductor laser device according to the fifth embodiment of the present invention.

The element region of the GaN-based semiconductor laser device of FIG. 16 is formed on the GaN-based semiconductor layer formed by the manufacturing process of FIG. As shown in FIG. 16, on a sapphire substrate 1, a low-temperature buffer layer 2 made of undoped Ga _0.5 Al _0.5 N having a thickness of 200 mm, an undoped GaN layer 8A having a thickness of 3 μm, and SiO _{2 having} a thickness of 1.0 μm. The pattern 5A is formed in order.

The pattern 5A has a circular planar shape and is arranged as shown in FIG. 5 or FIG. The length W ₅ of the diagonal line of the pattern 5A is 15 μm, and the pitch W ₆ is 20 μm.

  An undoped regrowth GaN layer 9A having a thickness of 20 μm is formed on the buffer layer 2 and the pattern 5A between the island-shaped GaN layer 8A and the pattern 5A formed on the GaN layer 8A. .

On the regrown GaN layer 9A, an n-GaN layer 20 having a thickness of 4.5 μm and an n-crack preventing layer 21 having a thickness of 0.25 μm are sequentially formed. The n-crack prevention layer 20 is formed by alternately stacking 21 pairs of Al _0.07 Ga _0.93 N having a thickness of 60 mm and n-GaN layers having a thickness of 60 mm. On the n-crack preventing layer 21, an n-cladding layer 22 made of Al _0.07 Ga _0.93 N having a thickness of 1.0 μm and an n-light guide layer 23 made of GaN having a thickness of 0.1 μm are sequentially formed. . On the n-light guide layer 23, an n-multiple quantum well active layer (hereinafter referred to as MQW active layer) 24 made of InGaN is formed. The n-MQW active layer 24 has a multiple quantum well structure in which a barrier layer made of In _0.02 Ga _0.98 N having a thickness of 100 mm and three quantum well layers made of In _0.13 Ga _0.87 N having a thickness of 50 mm are alternately stacked. Have

On the n-MQW active layer 24, a p-carrier block layer 25 made of Al _0.2 Ga _0.8 N having a thickness of 200 mm and a p-light guide layer 26 made of GaN having a thickness of 0.1 μm are formed. On the p-light guide layer 26, an n-AlGaN current blocking layer 27 made of Al _0.07 Ga _0.93 N having a stripe-shaped opening and having a thickness of about 0.5 μm is formed. A p-cladding layer 28 made of Al _0.07 Ga _0.93 N having a thickness of 0.5 μm is formed on the p-light guide layer 26 in the stripe-shaped opening. The p-cladding layer 28 forms a ridge portion having a width of 3 μm, and is formed avoiding the region above the pattern 5A. A p-contact layer 29 made of GaN having a thickness of 0.05 μm is formed on the n-AlGaN current blocking layer 27 and the p-cladding layer 28.

  A partial region from the p-contact layer 29 to the n-GaN layer 20 is removed by etching, and the n-GaN layer 20 is exposed. A p-electrode 30 is formed on the p-contact layer 29, and an n-electrode 31 is formed on the exposed upper surface of the n-GaN layer 20.

  The semiconductor laser element of FIG. 16 is formed by, for example, MOCVD (metal organic chemical vapor deposition). Table 1 shows the composition, film thickness, and growth temperature of each layer 2, 5A, 8A, 9A, 20 to 29 of the semiconductor laser device of FIG.

  Si is used as the n-type dopant, and Mg is used as the p-type dopant. As shown in Table 1, the growth temperature of the buffer layer 2 is 600 ° C., and the GaN layer 8A, the regrown GaN layer 9A, the n-crack preventing layer 21, the n-cladding layer 22, the n-light guide layer 23, p The growth temperature of the light guide layer 26, the n-AlGaN current blocking layer 27, the p-cladding layer 28 and the p-contact layer 29 is 1080 ° C. The growth temperature of the n-MQW active layer 24 and the p-carrier block layer 25 is 800 ° C.

When the buffer layer 2 is grown, TMG (trimethylgallium), TMA (trimethylaluminum), and NH ₃ are used as source gases. During the growth of the GaN layer 8A and the regrown GaN layer 9A, TMG and NH ₃ are used as source gases. When the n-GaN layer 20 and the n-light guide layer 23 are grown, TMG and NH ₃ are used as source gases and SiH ₄ is used as a dopant gas. When growing the n-crack prevention layer 21, the n-cladding layer 22, and the n-AlGaN current blocking layer 27, TMG, TMA, and NH ₃ are used as source gases, and SiH ₄ is used as a dopant gas.

During growth of the n-MQW active layer 24, TEG (triethylgallium), TMI (trimethylindium), and NH ₃ are used as source gases, and SiH ₄ is used as a dopant gas. During growth of the p-carrier block layer 25 and the p-cladding layer 28, TMG, TMA, and NH ₃ are used as source gases, and Cp ₂ Mg (cyclopentadienyl magnesium) is used as a dopant gas. When the p-light guide layer 26 and the p-contact layer 29 are grown, TMG and NH ₃ are used as source gases and Cp ₂ Mg is used as a dopant gas.

  The refractive index of the n-MQW active layer 24 is higher than the refractive indexes of the n-clad layer 22 and the p-clad layer 28, and the refractive indexes of the n-light guide layer 23 and the p-light guide layer 26 are n-MQW. It is lower than the refractive index of the active layer 24 and higher than the refractive indexes of the n-cladding layer 22 and the p-cladding layer 28.

  Since the p-cladding layer 28 is formed so as to avoid the region above the pattern 5A, the light emitting region of the semiconductor laser element can be formed in a region having few threading dislocations, and leakage current and impurity diffusion in the semiconductor laser device are suppressed. This can improve the characteristics of the semiconductor laser device. The longitudinal direction of the p-cladding layer 28 can be formed along the α direction and the β direction in FIG. 5 and along the φ direction, the γ direction, and the θ direction in FIG. Further, a hexagonal pattern may be used in place of the circular pattern 5A. In this case, the hexagonal pattern 5 is arranged as shown in FIGS. In the example of FIG. 2, the p-cladding layer 28 can be formed along either the α direction or β direction of the longitudinal direction, and in the example of FIG. 3, it is formed along any of the φ direction, the γ direction, or the θ direction. .

It is typical process sectional drawing which shows the manufacturing method of the GaN-type semiconductor laser element in 1st Example of this invention. It is a top view which shows an example of the matrix arrangement | sequence of a hexagonal pattern. It is a top view which shows the other example of the matrix arrangement | sequence of a hexagonal pattern. It is a figure for demonstrating the threading dislocation of the GaN layer regrown. It is a top view which shows an example of the matrix arrangement | sequence of a circular pattern. It is a top view which shows the other example of the matrix arrangement | sequence of a circular pattern. It is a conceptual diagram which shows the threading dislocation of the GaN layer regrown on the circular pattern. It is typical process sectional drawing which shows the formation method of the GaN-type semiconductor layer by the 2nd Example of this invention. It is a conceptual diagram which shows the threading dislocation of the GaN layer regrown on the circular GaN layer. It is a conceptual diagram which shows the threading dislocation of the GaN layer regrown on the hexagonal GaN layer. It is typical process sectional drawing which shows the formation method of the GaN-type semiconductor layer by the 3rd Example of this invention. It is a conceptual diagram which shows the threading dislocation of the GaN layer regrown in the circular mask on a circular GaN layer. It is a conceptual diagram which shows the threading dislocation of the GaN layer regrown on the hexagonal GaN layer and the pattern. It is typical process sectional drawing which shows the formation method of the GaN-type semiconductor layer by the 4th Example of this invention. It is a top view for demonstrating the etching area | region in the manufacturing process of FIG. It is a typical sectional view of a GaN system semiconductor laser device by the 5th example of the present invention. It is a conceptual diagram for demonstrating the threading dislocation of the GaN layer formed by the conventional lateral growth method. It is a conceptual diagram for demonstrating the threading dislocation of the GaN layer formed by the other conventional lateral growth method.

Explanation of symbols

1 Sapphire substrate 2 Buffer layer 3, 8, 8A GaN layer 5 Hexagonal pattern 5A Circular pattern 6, 9, 9A, 14 Regrown GaN layer

Claims (25)

A concavo-convex pattern in which a plurality of convex portions scattered in an island shape on the surface of the base made of the first nitride-based semiconductor layer or substrate are two-dimensionally arranged along three directions forming an angle of 60 ° with each other. And forming a second nitride-based semiconductor layer on the concave-convex pattern. The concavo-convex pattern is formed on a surface of the base by forming a plurality of crystal growth inhibition layers on the base made of the first nitride-based semiconductor layer as the plurality of convex portions. 2. The method for forming a nitride-based semiconductor layer according to 1. Forming the concavo-convex pattern on the surface of the base by forming a plurality of nitride-based semiconductor layers on the base made of the first nitride-based semiconductor layer or substrate as the plurality of convex portions. The method for forming a nitride-based semiconductor layer according to claim 1. The method for forming a nitride-based semiconductor layer according to claim 1, wherein the plurality of convex portions are circular or polygonal. 5. The method for forming a nitride-based semiconductor layer according to claim 4, wherein the polygon is a hexagon. A concavo-convex pattern in which a plurality of convex portions scattered in an island shape are two-dimensionally arranged along three directions forming an angle of 60 ° with each other on the surface of the base made of the first nitride-based semiconductor layer or substrate And a second nitride-based semiconductor layer is formed on the concavo-convex pattern. The nitride-based semiconductor according to claim 6, wherein the plurality of protrusions are a plurality of crystal growth blocking layers formed on the base made of the first nitride-based semiconductor layer. The nitride-based semiconductor according to claim 6, wherein the plurality of convex portions are a plurality of nitride-based semiconductor layers formed on the base made of the first nitride-based semiconductor layer or the substrate. . 7. The plurality of convex portions are a plurality of nitride-based semiconductor layers and a crystal growth blocking layer stacked on the base made of the first nitride-based semiconductor layer or substrate. Nitride based semiconductor. A concavo-convex pattern consisting of a plurality of convex portions scattered in an island shape is formed on the surface of a base made of a first nitride semiconductor layer or substrate, and a second nitride semiconductor layer is formed on the concavo-convex pattern And forming a third nitride-based semiconductor layer including an element region on the second nitride-based semiconductor layer. 11. The nitride-based semiconductor according to claim 10, wherein the third nitride-based semiconductor layer includes an n-type contact layer, an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type contact layer. Device manufacturing method. 12. The method for manufacturing a nitride semiconductor device according to claim 10, wherein the second nitride semiconductor layer is an undoped layer. 13. The method for manufacturing a nitride semiconductor device according to claim 12, wherein the second nitride semiconductor layer is a GaN layer. The plurality of protrusions are two-dimensionally arranged along a plurality of directions, and a light emitting region extending along any one of the plurality of directions is formed in the element region above the plurality of protrusions. The method for manufacturing a nitride-based semiconductor device according to claim 10, wherein: A concavo-convex pattern in which a plurality of convex portions scattered in an island shape on the surface of the base made of the first nitride-based semiconductor layer or substrate are two-dimensionally arranged along three directions forming an angle of 60 ° with each other. Forming a second nitride-based semiconductor layer on the concavo-convex pattern, and forming a third nitride-based semiconductor layer including an element region on the second nitride-based semiconductor layer. A method for manufacturing a nitride semiconductor device. A concavo-convex pattern composed of a plurality of convex portions scattered in an island shape is formed on the surface of the base made of the first nitride-based semiconductor layer or substrate, and a second nitride-based semiconductor layer is formed on the concavo-convex pattern. A nitride-based semiconductor device, wherein a third nitride-based semiconductor layer including an element region is formed on the second nitride-based semiconductor layer. The nitride semiconductor according to claim 16, wherein the third nitride semiconductor layer includes an n-type contact layer, an n-type cladding layer, an active layer, a p-type cladding layer, and a p-type contact layer. element. The method for manufacturing a nitride-based semiconductor element according to claim 16 or 17, wherein the second nitride-based semiconductor layer is an undoped layer. 19. The method for manufacturing a nitride semiconductor device according to claim 18, wherein the second nitride semiconductor layer is a GaN layer. The plurality of protrusions are two-dimensionally arranged along a plurality of directions, and the element region emits light extending along any one of the plurality of directions in the element region above the plurality of protrusions. 20. The nitride semiconductor device according to claim 16, further comprising a region. A concavo-convex pattern formed by two-dimensionally arranging a plurality of convex portions scattered in an island shape on the surface of the base made of the first nitride-based semiconductor layer or substrate along three directions forming an angle of 60 ° with each other The second nitride semiconductor layer is formed on the concave-convex pattern, and the third nitride semiconductor layer including the element region is formed on the second nitride semiconductor layer. A nitride-based semiconductor device characterized by the above. The plurality of protrusions are two-dimensionally arranged along a plurality of directions, and the element region emits light extending along any one of the plurality of directions in the element region above the plurality of protrusions. The nitride semiconductor device according to claim 21, further comprising a region. The nitride semiconductor device according to claim 22, wherein the light emitting region constitutes a resonator. Forming a crystal growth blocking layer on a first nitride semiconductor layer or an underlying surface comprising a substrate; and forming a second nitride semiconductor layer having a region with many threading dislocations on the crystal growth blocking layer And a method for manufacturing a nitride-based semiconductor device. The method for manufacturing a nitride-based semiconductor device according to claim 24, further comprising a step of forming a resonator while avoiding a region where there are many threading dislocations.

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