Large bevel angle heterogeneous substrate-gallium nitride composite structure and growth method thereof

Abstract

The present invention discloses a large bevel angle heterogeneous substrate-gallium nitride composite structure and a growth method thereof. The method comprises: growing an island-shaped gallium nitride buffer layer in the steps of a large bevel angle heterogeneous substrate; growing a two-dimensional gallium nitride layer on the large bevel angle heterogeneous substrate, and making the two-dimensional gallium nitride layer fill the steps on the large bevel angle heterogeneous substrate; growing a three-dimensional island gallium nitride layer on the two-dimensional gallium nitride layer; merging the three-dimensional island gallium nitride layer and growing gallium nitride materials. The method provided by the present invention adopts a novel "buffer layer-two-dimensional-three-dimensional bottom structure" heteroepitaxial growth method, which overcomes the technical problem that the growth morphology is difficult to be flattened due to the large bevel angle, thereby giving full play to the advantages and characteristics of the epitaxial film of the large bevel angle substrate.

Description

Technical Field

[0001] The present invention particularly relates to a large bevel angle heterogeneous substrate-gallium nitride composite structure and a growth method thereof, belonging to the technical field of semiconductors. Background Art

[0002] At present, the epitaxial growth of GaN materials is divided into homoepitaxial and heteroepitaxial. Homoepitaxial growth is performed on GaN substrates. The GaN epitaxial film on it has high flatness, and the surface generally presents a narrow step flow morphology, and the crystal quality is very good. Heteroepitaxial growth is performed on substrates such as sapphire. The GaN epitaxial film on it is affected by the substrate bevel angle, and the flatness and crystal quality are inferior to homoepitaxial growth.

[0003] In order to improve the quality, the industry uses heterogeneous substrates with very small bevel angles (the bevel angle of sapphire substrates is generally 0.2°). This makes it easy to obtain gallium nitride epitaxial films with high flatness, but the problem is that the surface generally presents a wider step morphology, which is quite different from the actual homoepitaxial film. The use of heterogeneous substrates with larger bevel angles can solve the above problems, because as the bevel angle increases, the step spacing becomes narrower accordingly, making the grown gallium nitride material closer to the characteristics of the homoepitaxial film itself. However, the traditional "buffer layer-three-dimensional bottom structure" heteroepitaxial growth method is only suitable for substrates with very small bevel angles, and cannot meet the requirements of the smooth growth of narrow steps with large bevel angles, so that gallium nitride materials with high flatness cannot be grown, affecting the quality of substrates with large bevel angles.

[0004] For example, the existing process for epitaxially growing gallium nitride materials on a sapphire substrate with a small bevel angle is as follows: Figure 1 As shown, usually about 25nm of low-temperature GaN polycrystal is first deposited on a sapphire substrate with a small bevel angle as a buffer layer, and then the buffer layer is annealed and recrystallized under the protection of ammonia. At this time, the buffer layer will form aggregate nuclei at the steps to become small islands; then about 500nm of GaN is grown. Under this condition, the growth mode of GaN is three-dimensional longitudinal growth, and the underlying structure is completed; then merging and rapid growth of GaN materials are carried out; due to the small bevel angle, the three-dimensionally grown gallium nitride can develop on a larger step platform, and because the large islands of three-dimensional gallium nitride are closely spaced, they can be well merged to form a gallium nitride material with high flatness.

[0005] If the sapphire substrate with a small bevel angle is replaced with a sapphire substrate with a large bevel angle and the epitaxial growth of gallium nitride material is performed (such as Figure 2 As shown in the figure, due to the narrow and deep steps of the sapphire substrate with a large bevel angle, a small platform will be formed during the three-dimensional GaN growth. As a result, the three-dimensional GaN islands are not merged enough due to the large distance between them, so that the final GaN material cannot form a flat surface. Summary of the invention

[0006] The main purpose of the present invention is to provide a large bevel angle heterogeneous substrate-gallium nitride composite structure and a growth method thereof to overcome the deficiencies in the prior art.

[0007] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention includes:

[0008] An embodiment of the present invention provides a method for epitaxially growing a gallium nitride material on a heterogeneous substrate with a large bevel angle, comprising:

[0009] 1) Growing an island-shaped GaN buffer layer within the steps of a heterogeneous substrate with a large bevel angle;

[0010] 2) growing a two-dimensional gallium nitride layer on the large off-angle heterogeneous substrate, and allowing the two-dimensional gallium nitride layer to fill the steps on the large off-angle heterogeneous substrate;

[0011] 3) growing a three-dimensional island-shaped gallium nitride layer on the two-dimensional gallium nitride layer;

[0012] 4) Merging three-dimensional island-shaped gallium nitride layers and growing gallium nitride materials.

[0013] In some more specific embodiments, the method specifically comprises:

[0014] 1) First, a low-temperature gallium nitride polycrystal is grown on a heterogeneous substrate with a large bevel angle at 500-600° C. and 400-600 Torr as a gallium nitride buffer layer, and then the gallium nitride buffer layer is annealed in a protective gas atmosphere at 1020-1080° C. and 400-600 Torr, so that the gallium nitride buffer layer is gathered at the step of the heterogeneous substrate with a large bevel angle, thereby forming an island-shaped gallium nitride buffer layer;

[0015] 2) growing a two-dimensional gallium nitride layer on a heterogeneous substrate with a large bevel angle at a growth rate of 3-10 nm / min at 1020-1080° C. and 50-200 Torr until the two-dimensional gallium nitride layer fills up the steps on the heterogeneous substrate with a large bevel angle;

[0016] 3) growing a three-dimensional island-shaped gallium nitride layer on the two-dimensional gallium nitride layer at 980-1050° C. and 400-600 Torr;

[0017] 4) The three-dimensional island-shaped gallium nitride layer is merged and the gallium nitride material is rapidly grown under the conditions of 1050-1100° C. and 100-300 Torr.

[0018] The embodiment of the present invention also provides a large bevel angle heterogeneous substrate-gallium nitride composite structure grown by the method.

[0019] Compared with the prior art, the advantages of the present invention include:

[0020] The embodiment of the present invention provides a method for epitaxially growing a gallium nitride material on a heterogeneous substrate with a large bevel angle. The growth process is simple and the growth conditions are easy to adjust. A heterogeneous substrate-gallium nitride composite structure with a large bevel angle and higher surface flatness can be obtained.

[0021] The embodiment of the present invention provides a method for epitaxially growing gallium nitride materials on a heterogeneous substrate with a large bevel angle, which adopts a novel heteroepitaxial growth method of "buffer layer-two-dimensional-three-dimensional underlying structure", thereby overcoming the technical problem of difficulty in flattening the growth morphology caused by the large bevel angle, thereby giving full play to the advantages of the epitaxial film of the substrate with a large bevel angle. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic flow chart of a method for epitaxially growing gallium nitride material on a sapphire substrate with a small bevel angle in the prior art;

[0023] Figure 2 This is a schematic flow chart of the method for epitaxially growing gallium nitride material on a sapphire substrate with a large bevel angle in Comparative Example 1;

[0024] Figure 3 It is a schematic flow chart of a method for epitaxially growing a gallium nitride material on a sapphire substrate with a large bevel angle in Embodiment 1 of the present invention;

[0025] Figure 4 is a surface morphology of a large bevel angle heterogeneous substrate-gallium nitride composite structure obtained in comparative example 1;

[0026] Figure 5 is a surface morphology image of a large bevel angle heterogeneous substrate-gallium nitride composite structure obtained in Example 1;

[0027] Figure 6 This is an atomic force characterization image of a large bevel angle heterogeneous substrate-GaN composite structure obtained in Example 1;

[0028] Figure 7 This is an atomic force characterization image of a large bevel angle heterogeneous substrate-gallium nitride composite structure obtained in Example 1;

[0029] Figure 8 is a rocking curve diagram of a large bevel angle heterogeneous substrate-gallium nitride composite structure obtained in comparative example 1;

[0030] Fig. 9 3 is a rocking curve diagram of the large bevel angle heterogeneous substrate-gallium nitride composite structure obtained in Example 1. DETAILED DESCRIPTION

[0031] In view of the deficiencies in the prior art, the inventor of this case has proposed the technical solution of the present invention after long-term research and extensive practice. The technical solution, its implementation process and principle will be further explained as follows.

[0032] The embodiment of the present invention provides a method for epitaxially growing a gallium nitride material on a heterojunction substrate with a large bevel angle. Combining the surface condition of the heterojunction substrate with a large bevel angle and the characteristics of the epitaxial growth of the gallium nitride material, a novel "buffer layer-two-dimensional-three-dimensional underlying structure" heteroepitaxial growth method is proposed to overcome the technical problem of the difficulty in flattening the growth morphology caused by the large bevel angle, thereby giving full play to the advantages of the epitaxial film of the substrate with a large bevel angle.

[0033] An embodiment of the present invention provides a method for epitaxially growing a gallium nitride material on a heterogeneous substrate with a large bevel angle, comprising:

[0034] 1) Growing an island-shaped GaN buffer layer within the steps of a heterogeneous substrate with a large bevel angle;

[0035] 2) growing a two-dimensional gallium nitride layer on the large off-angle heterogeneous substrate, and allowing the two-dimensional gallium nitride layer to fill the steps on the large off-angle heterogeneous substrate;

[0036] 3) growing a three-dimensional island-shaped gallium nitride layer on the two-dimensional gallium nitride layer;

[0037] 4) Merging three-dimensional island-shaped gallium nitride layers and growing gallium nitride materials.

[0038] Furthermore, the step 1) specifically includes: first growing a gallium nitride buffer layer on a large bevel angle heterogeneous substrate, and then annealing the gallium nitride buffer layer under a protective gas atmosphere so that the gallium nitride buffer layer is gathered at the steps of the large bevel angle heterogeneous substrate, thereby forming an island-shaped gallium nitride buffer layer.

[0039] Furthermore, the growth temperature of the gallium nitride buffer layer is 500-600° C. and the growth pressure is 400-600 Torr.

[0040] Furthermore, the annealing treatment temperature is 1020-1080° C., and the protective gas includes ammonia.

[0041] Furthermore, the growth temperature of the two-dimensional gallium nitride layer is 1020-1080° C. and the growth pressure is 50-200 Torr.

[0042] Furthermore, the growth rate of the two-dimensional gallium nitride layer is 3-10 nm / min.

[0043] Furthermore, the two-dimensional gallium nitride layer has a continuous and flat surface.

[0044] Furthermore, the growth temperature of the three-dimensional island-shaped gallium nitride layer is 980-1050° C. and the growth pressure is 400-600 Torr.

[0045] Furthermore, the bevel angle of the large bevel angle heterogeneous substrate is greater than 0.5°.

[0046] Furthermore, the large bevel angle heterogeneous substrate includes a sapphire substrate.

[0047] In some more specific embodiments, the method specifically comprises:

[0048] 1) First, a low-temperature gallium nitride polycrystal is grown on a heterogeneous substrate with a large bevel angle at 500-600° C. and 400-600 Torr as a gallium nitride buffer layer, and then the gallium nitride buffer layer is annealed in a protective gas atmosphere at 1020-1080° C. and 400-600 Torr, so that the gallium nitride buffer layer is gathered at the step of the heterogeneous substrate with a large bevel angle, thereby forming an island-shaped gallium nitride buffer layer;

[0049] 2) growing a two-dimensional gallium nitride layer on a heterogeneous substrate with a large bevel angle at a growth rate of 3-10 nm / min at 1020-1080° C. and 50-200 Torr until the two-dimensional gallium nitride layer fills up the steps on the heterogeneous substrate with a large bevel angle;

[0050] 3) growing a three-dimensional island-shaped gallium nitride layer on the two-dimensional gallium nitride layer at 980-1050° C. and 400-600 Torr;

[0051] 4) The three-dimensional island-shaped gallium nitride layer is merged and the gallium nitride material is rapidly grown under the conditions of 1050-1100° C. and 100-300 Torr.

[0052] The embodiment of the present invention also provides a large bevel angle heterogeneous substrate-gallium nitride composite structure grown by the method.

[0053] Furthermore, the large bevel angle heterogeneous substrate-gallium nitride composite structure has a flat surface.

[0054] The technical solution, its implementation process and principle will be further explained below in conjunction with specific embodiments. Unless otherwise specified, the raw material ratio and detection method of the gallium nitride layer in the embodiments of the present invention can be those known to those skilled in the art.

[0055] Example 1

[0056] A heteroepitaxial growth method based on a "buffer layer-two-dimensional-three-dimensional underlying structure" includes:

[0057] 1) placing a high-bevel angle sapphire substrate with a bevel angle of 1° in an epitaxial growth chamber, adjusting the growth temperature in the growth chamber to 500° C. and the growth pressure to 600 torr, and depositing a 25 nm low-temperature GaN buffer layer on the high-bevel angle sapphire substrate;

[0058] 2) The growth temperature in the growth chamber is raised to 1020° C., the growth pressure is maintained at 400 torr, and the low-temperature GaN buffer layer is annealed for 4 minutes. At this time, the low-temperature GaN buffer layer is aggregated at the step to form an island shape;

[0059] 3) Raising the growth temperature in the growth chamber to 1040° C., reducing the growth pressure to 50 torr, and growing a 150 nm two-dimensional GaN layer on the high-bevel angle sapphire substrate at a growth rate of 3 nm / min until the narrow step on the high-bevel angle sapphire substrate is filled to the top of the step platform;

[0060] 4) The growth temperature in the growth chamber is cooled to 980°C, the growth pressure is increased to 400 torr, and a 500nm 3D GaN layer is grown on the 2D GaN layer. At this time, since the narrow step platform has been broken through, the grown 3D GaN islands are developed with a smaller spacing, thereby forming a new underlying structure;

[0061] 5) The growth pressure in the growth chamber is reduced to 100 torr, the growth temperature is increased to 1050°C, and the three-dimensional GaN layer is merged and the GaN material is rapidly grown. The thickness of the GaN material is 2 μm, and finally a large bevel angle heterogeneous substrate-GaN composite structure with a flat surface morphology is obtained, and its crystal quality is correspondingly improved.

[0062] Example 2

[0063] See also Figure 3 , a heteroepitaxial growth method based on a "buffer layer-two-dimensional-three-dimensional underlying structure" includes:

[0064] 1) placing a high-bevel angle sapphire substrate with a bevel angle of 1° in an epitaxial growth chamber, adjusting the growth temperature in the growth chamber to 530° C. and the growth pressure to 500 torr, and depositing a 25 nm low-temperature GaN buffer layer on the high-bevel angle sapphire substrate;

[0065] 2) Raising the growth temperature in the growth chamber to 1040° C. and annealing the low-temperature GaN buffer layer for 5 minutes, at which time the low-temperature GaN buffer layer aggregates at the step to form an island shape;

[0066] 3) Raising the growth temperature in the growth chamber to 1060° C., reducing the growth pressure to 100 torr, and growing a 150 nm two-dimensional GaN layer on the high-bevel angle sapphire substrate at a growth rate of 5 nm / min until the narrow steps on the high-bevel angle sapphire substrate are filled to the top of the step platform;

[0067] 4) The growth temperature in the growth chamber is cooled to 1000°C, the growth pressure is increased to 500 torr, and a 500nm 3D GaN layer is grown on the 2D GaN layer. At this time, since the narrow step platform has been broken through, the grown 3D GaN islands are developed with a smaller spacing, thereby forming a new underlying structure;

[0068] 5) The growth pressure in the growth chamber is reduced to 200 torr, the growth temperature is increased to 1080°C, and the three-dimensional GaN layer is merged and the GaN material is rapidly grown. The thickness of the GaN material is 2 μm, and finally a large bevel angle heterogeneous substrate-GaN composite structure with a flat surface morphology is obtained, and its crystal quality is also improved accordingly.

[0069] Example 3

[0070] See also Figure 3 , a heteroepitaxial growth method based on a "buffer layer-two-dimensional-three-dimensional underlying structure" includes:

[0071] 1) placing a high-bevel angle sapphire substrate with a bevel angle of 1° in an epitaxial growth chamber, adjusting the growth temperature in the growth chamber to 600° C. and the growth pressure to 400 torr, and depositing a 25 nm low-temperature GaN buffer layer on the high-bevel angle sapphire substrate;

[0072] 2) Raising the growth temperature in the growth chamber to 1080° C., maintaining the growth pressure at 500 torr, and annealing the low-temperature GaN buffer layer for 5 minutes, at which time the low-temperature GaN buffer layer aggregates at the step to form an island shape;

[0073] 3) Raising the growth temperature in the growth chamber to 1080° C., reducing the growth pressure to 200 torr, and growing a 150 nm two-dimensional GaN layer on the high-bevel angle sapphire substrate at a growth rate of 10 nm / min until the narrow step on the high-bevel angle sapphire substrate is filled to the top of the step platform;

[0074] 4) The growth temperature in the growth chamber is cooled to 1050°C, the growth pressure is increased to 600 torr, and a 500nm 3D GaN layer is grown on the 2D GaN layer. At this time, since the narrow step platform has been broken through, the grown 3D GaN islands are developed with a smaller spacing, thereby forming a new underlying structure;

[0075] 5) The growth pressure in the growth chamber is reduced to 300 torr, the growth temperature is increased to 1100°C, and the three-dimensional GaN layer is merged and the GaN material is rapidly grown. The thickness of the GaN material is 2 μm, and finally a large bevel angle heterogeneous substrate-GaN composite structure with a flat surface morphology is obtained, and its crystal quality is also improved accordingly.

[0076] Comparative Example 1

[0077] A heteroepitaxial growth method of "buffer layer-three-dimensional underlying structure"

[0078] 1) placing a high-bevel angle sapphire substrate with a bevel angle of 1° in an epitaxial growth chamber, adjusting the growth temperature in the growth chamber to 530° C. and the growth pressure to 500 torr, so as to deposit a 25 nm low-temperature GaN buffer layer on the high-bevel angle sapphire substrate;

[0079] 2) Raising the growth temperature in the growth chamber to 1040° C. and annealing the low-temperature GaN buffer layer for 5 minutes, at which time the low-temperature GaN buffer layer aggregates at the step to form an island shape;

[0080] 3) lowering the growth temperature in the growth chamber to 1000° C., increasing the growth pressure to 500 torr, and growing a 500 nm three-dimensional GaN layer on the two-dimensional GaN layer;

[0081] 4) The growth pressure in the growth chamber is reduced to 200 torr, the growth temperature is increased to 1080°C, and the three-dimensional GaN layer is merged and the GaN material is rapidly grown. The thickness of the GaN material is 2 μmm, and finally a large bevel angle heterogeneous substrate-gallium nitride composite structure is obtained.

[0082] The large bevel angle heterogeneous substrate-GaN composite structures obtained in Comparative Example 1 and Example 1 are respectively Sample 1 and Sample 2. Optical microscopy, atomic force microscopy and X-ray diffraction tests are performed on Sample 1 and Sample 2, respectively. The test results are as follows: Figure 4-Figure 9 As shown, the test results of the large bevel angle heterogeneous substrate-gallium nitride composite structure in Examples 2-3 are basically consistent with the test results of the large bevel angle heterogeneous substrate-gallium nitride composite structure in Example 1.

[0083] Depend on Figure 4-Figure 9It can be seen from the test results that the surface morphology of sample 2 is smooth, and its surface roughness Ra value is increased from 1.3nm of sample 1 to 0.3nm, and the corresponding half width of the (002) plane is also reduced from about 250 arc seconds to 150 arc seconds. The crystal quality is greatly improved. It can be seen that the heteroepitaxial growth method based on the "buffer layer-two-dimensional-three-dimensional underlying structure" provided by the embodiment of the present invention overcomes the technical problem of difficult flat growth morphology caused by large bevel angles, and gives full play to the advantages of epitaxial films on substrates with large bevel angles.

[0084] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for epitaxially growing gallium nitride material on a heterogeneous substrate with a large bevel angle, characterized in that include: 1) Growing an island-shaped gallium nitride buffer layer in a step of a heterogeneous substrate with a large bevel angle, wherein the bevel angle of the heterogeneous substrate with a large bevel angle is greater than 0.5°; 2) growing a two-dimensional gallium nitride layer on the large off-angle heterogeneous substrate, and allowing the two-dimensional gallium nitride layer to fill the steps on the large off-angle heterogeneous substrate; 3) growing a three-dimensional island-shaped gallium nitride layer on the two-dimensional gallium nitride layer; 4) Merging three-dimensional island-shaped gallium nitride layers and growing gallium nitride materials.

2. The method according to claim 1, characterized in that The step 1) specifically includes: firstly growing a gallium nitride buffer layer on a large off-angle heterogeneous substrate, and then annealing the gallium nitride buffer layer under a protective gas atmosphere so that the gallium nitride buffer layer is aggregated at the steps of the large off-angle heterogeneous substrate, thereby forming an island-shaped gallium nitride buffer layer.

3. The method according to claim 2, characterized in that: The growth temperature of the gallium nitride buffer layer is 500-600° C. and the growth pressure is 400-600 Torr.

4. The method according to claim 2, characterized in that: The annealing treatment temperature is 1020-1080° C., and the protective gas includes ammonia.

5. The method according to claim 1, characterized in that: The growth temperature of the two-dimensional gallium nitride layer is 1020-1080° C. and the growth pressure is 50-200 Torr.

6. The method according to claim 1, characterized in that: The growth rate of the two-dimensional gallium nitride layer is 3-10 nm / min.

7. The method according to claim 1, characterized in that: The two-dimensional gallium nitride layer has a continuous and flat surface.

8. The method according to claim 1, characterized in that: The growth temperature of the three-dimensional island-shaped gallium nitride layer is 980-1050° C. and the growth pressure is 400-600 Torr.

9. The method according to claim 1, characterized in that: The large off-angle foreign substrate includes a sapphire substrate.

10. The method according to claim 1, characterized in that Specifically include: 1) First, a low-temperature gallium nitride polycrystal is grown on a heterogeneous substrate with a large bevel angle at 500-600° C. and 400-600 Torr as a gallium nitride buffer layer, and then the gallium nitride buffer layer is annealed in a protective gas atmosphere at 1020-1080° C. and 400-600 Torr, so that the gallium nitride buffer layer is gathered at the step of the heterogeneous substrate with a large bevel angle, thereby forming an island-shaped gallium nitride buffer layer; 2) growing a two-dimensional gallium nitride layer on the heterogeneous substrate with a large bevel angle at a growth rate of 3-10 nm / min at 1020-1080 ° C and 50-200 Torr until the two-dimensional gallium nitride layer fills the steps on the heterogeneous substrate with a large bevel angle; 3) growing a three-dimensional island-shaped gallium nitride layer on the two-dimensional gallium nitride layer at 980-1050° C. and 400-600 Torr; 4) The merging of three-dimensional island-shaped GaN layers and the rapid growth of GaN materials are carried out under the conditions of 1050-1100 °C and 100-300 Torr.

11. A large off-angle foreign substrate-gallium nitride composite structure grown by the method according to any one of claims 1 to 10.

12. The large bevel angle heterogeneous substrate-gallium nitride composite structure according to claim 11, characterized in that: The large-bevel-angle heterogeneous substrate-gallium nitride composite structure has a flat surface.

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