Growth substrate, preparation method thereof and transistor

Abstract

The invention provides a growth substrate, a preparation method thereof and a transistor, and belongs to the field of power electronics. The growth substrate comprises a substrate, a boron nitride layer and a graphene layer, the boron nitride layer and the graphene layer are sequentially stacked on the substrate, and the surface, away from the substrate, of the graphene layer is provided with a plurality of mask patterns arranged at intervals. According to the embodiment of the invention, the dislocation density between the substrate and the GaN epitaxial layer is improved, the substrate can be recycled for multiple times, and the use cost is reduced.

Description

Technical Field

[0001] The present disclosure relates to the field of power electronics, and in particular to a growth substrate and a preparation method thereof, and a transistor. Background Art

[0002] High Electron Mobility Transistor (HEMT) is a heterojunction field effect transistor that is widely used in various electrical appliances.

[0003] In the related art, transistors usually include a sapphire substrate and a GaN epitaxial layer formed on the substrate. Due to the lattice mismatch between the sapphire substrate and the GaN epitaxial layer, the GaN epitaxial layer grown on the sapphire substrate has a large dislocation density, making it difficult to exert the performance of GaN-based transistors. Therefore, a GaN substrate is usually used to grow a GaN epitaxial layer to improve the dislocation density between the substrate and the GaN epitaxial layer.

[0004] However, after the GaN substrate is etched and peeled off, its surface is severely damaged and cannot be recycled; most GaN substrates are 2 inches, and it is difficult to ensure both quality and shape for larger GaN substrates. Therefore, the cost of using GaN substrates is relatively high. Summary of the invention

[0005] The embodiments of the present disclosure provide a growth substrate and a preparation method thereof and a transistor, which can improve the dislocation density between the substrate and the GaN epitaxial layer, and can be recycled multiple times to reduce the use cost. The technical solution is as follows:

[0006] In a first aspect, an embodiment of the present disclosure provides a growth substrate, comprising: a substrate, a boron nitride layer and a graphene layer, wherein the boron nitride layer and the graphene layer are sequentially stacked on the substrate, and a surface of the graphene layer away from the substrate has a plurality of mask patterns arranged at intervals.

[0007] In another implementation of the present disclosure, the cross-sectional shape of the mask pattern is polygonal or arcuate.

[0008] In another implementation of the present disclosure, the height of the mask pattern is 5 nm to 15 nm.

[0009] In another implementation of the present disclosure, a spacing between adjacent mask patterns is 10 μm to 50 μm.

[0010] In another implementation of the present disclosure, the thickness of the boron nitride layer is 1 nm to 3 nm.

[0011] In another implementation of the present disclosure, the growth substrate further includes a GaN base layer, and the GaN base layer is located on the surface of the graphene layer having the mask pattern.

[0012] In a second aspect, an embodiment of the present disclosure provides a method for preparing a growth substrate, the method comprising: providing a substrate; forming a boron nitride layer on the substrate; forming a graphene layer on the boron nitride layer, wherein a surface of the graphene layer away from the substrate has a plurality of mask patterns arranged at intervals.

[0013] In another implementation of the present disclosure, forming a boron nitride layer on the substrate includes: controlling the pressure of the reaction chamber to 50 torr to 100 torr, controlling the temperature in the reaction chamber to 1000°C to 1100°C, introducing ammonia and a boron source into the reaction chamber, adjusting the molar ratio of ammonia to the boron source to 1500 to 1600, and growing the boron nitride layer.

[0014] In another implementation of the present disclosure, after the graphene layer is formed on the boron nitride layer, it also includes: introducing 15 sccm to 20 sccm of Ga source and 20 slm to 30 slm of ammonia into the reaction chamber, controlling the temperature in the reaction chamber to 900°C to 950°C, and forming a GaN film on the surface of the mask pattern; introducing 40 sccm to 45 sccm of Ga source and 100 slm to 110 slm of ammonia into the reaction chamber, controlling the temperature in the reaction chamber to 1070°C to 1100°C, allowing the GaN film attached to the surface of the mask pattern to grow laterally, forming a GaN base layer covering each of the mask patterns.

[0015] In a third aspect, an embodiment of the present disclosure provides a transistor, comprising a growth substrate and an epitaxial layer as described above, wherein the epitaxial layer comprises a GaN high resistance layer, a GaN channel layer, an AlN insertion layer, an AlGaN barrier layer and a GaN cap layer sequentially stacked on the growth substrate.

[0016] The beneficial effects brought by the technical solution provided by the embodiments of the present disclosure include at least:

[0017] The growth substrate provided by the embodiment of the present disclosure includes a graphene layer and a boron nitride layer stacked on a substrate in sequence. A two-dimensional material boron nitride layer is used as an insertion layer. Since the two-dimensional material layers are bonded to each other through van der Waals forces, a plurality of mask patterns arranged at intervals are also provided on the graphene layer, so that the GaN epitaxial layer subsequently formed on the graphene layer can be deposited in the gaps between the mask patterns. Due to the presence of the graphene / boron nitride composite insertion layer, the lattice mismatch and thermal mismatch between the epitaxial layer and the substrate can be effectively alleviated, the crystal quality of the epitaxial layer can be improved, and the film stress of the epitaxial layer can be reduced, thereby solving the warping problem of large-size wafers. In addition, due to the presence of the two-dimensional material boron nitride layer, the separation between the substrate and the epitaxial layer can be achieved by simple mechanical peeling, so that the substrate can be reused, which is conducive to reducing production costs.

[0018] At the same time, the GaN epitaxial layer grown on the graphene layer will first adhere to the surface of the mask pattern; and, during the continuous growth process, the GaN material attached to the surface of the mask pattern will expand laterally from the edge of the graphene layer, and eventually cover the surface of the graphene layer. This lateral epitaxial growth method can avoid the crystal defects under the graphene layer, effectively reduce the dislocation density of the GaN epitaxial layer, and thus form a GaN epitaxial layer with better crystal quality above the graphene layer. The growth substrate provided by the embodiment of the present disclosure adopts an organic combination of van der Waals epitaxy and lateral epitaxy, which can not only realize the epitaxy of high-quality single-crystalline GaN epitaxial layers on the substrate, but also realize the recycling of the substrate, thereby reducing the production cost of the enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 is a schematic structural diagram of a growth substrate provided by an embodiment of the present disclosure;

[0021] Figure 2 is a partial schematic diagram of a growth substrate provided by an embodiment of the present disclosure;

[0022] Figure 3 is a flow chart of a method for preparing a growth substrate provided by an embodiment of the present disclosure;

[0023] Figure 4 is a diagram of a preparation state of a growth substrate provided by an embodiment of the present disclosure;

[0024] Figure 5It is a hierarchical schematic diagram of a transistor provided in an embodiment of the present disclosure.

[0025] The descriptions of the marks in the figure are as follows:

[0026] 10. Substrate;

[0027] 20. Boron nitride layer;

[0028] 30. graphene layer; 31. mask pattern;

[0029] 40. GaN base layer;

[0030] 51. GaN high resistance layer; 52. GaN channel layer; 53. AlN insertion layer; 54. AlGaN barrier layer; 55. GaN cap layer. DETAILED DESCRIPTION

[0031] In order to make the objectives, technical solutions and advantages of the present disclosure more clear, the embodiments of the present disclosure will be further described in detail below with reference to the accompanying drawings.

[0032] Unless otherwise defined, the technical terms or scientific terms used herein shall have the usual meanings understood by persons with ordinary skills in the field to which the present disclosure belongs. The words "first", "second", "third" and similar words used in the patent application specification and claims of the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, words such as "one" or "one" do not indicate a quantity limitation, but indicate the existence of at least one. Words such as "include" or "comprise" and similar words mean that the elements or objects appearing before "include" or "comprise" include the elements or objects listed after "include" or "comprise" and their equivalents, and do not exclude other elements or objects. Words such as "connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Up", "down", "left", "right", "top", "bottom" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0033] Figure 1 Schematic diagram of the structure of a growth substrate provided by an embodiment of the present disclosure. Figure 1 As shown, the growth substrate includes: a substrate 10, a boron nitride layer 20 and a graphene layer 30, wherein the boron nitride layer 20 and the graphene layer 30 are sequentially stacked on the substrate 10, and a surface of the graphene layer 30 away from the substrate 10 has a plurality of mask patterns 31 arranged at intervals.

[0034] The growth substrate provided by the embodiment of the present disclosure includes a graphene layer 30 and a boron nitride layer 20 sequentially stacked on a substrate 10. The two-dimensional material boron nitride layer 20 is used as an insertion layer. Since the two-dimensional material layers are bonded to each other through van der Waals forces, a plurality of mask patterns 31 arranged at intervals are also provided on the graphene layer 30, so that the GaN epitaxial layer subsequently formed on the graphene layer 30 can be deposited in the gaps between the mask patterns 31. Due to the presence of the graphene / boron nitride composite insertion layer, the lattice mismatch and thermal mismatch between the epitaxial layer and the substrate can be effectively alleviated, the crystal quality of the epitaxial layer can be improved, and the film stress of the epitaxial layer can be reduced, thereby solving the warping problem of large-size wafers. In addition, due to the presence of the two-dimensional material boron nitride layer 20, the separation between the substrate 10 and the epitaxial layer can be achieved by simple mechanical peeling, and the substrate 10 can be reused, which is conducive to reducing production costs.

[0035] At the same time, the GaN epitaxial layer grown on the graphene layer 30 will first adhere to the surface of the mask pattern 31; and, during the continuous growth process, the GaN material attached to the surface of the mask pattern 31 will begin to expand laterally from the edge of the graphene layer 30, and eventually cover the surface of the graphene layer 30. This lateral epitaxial growth method can avoid the crystal defects under the graphene layer 30, effectively reduce the dislocation density of the GaN epitaxial layer, and thus form a GaN epitaxial layer with better crystal quality above the graphene layer 30. The growth substrate provided by the embodiment of the present disclosure adopts an organic combination of van der Waals epitaxy and lateral epitaxy, which can not only realize the epitaxy of high-quality single-crystal GaN epitaxial layer on the substrate 10, but also realize the recycling of the substrate 10, thereby reducing the production cost of the enterprise.

[0036] Optionally, the cross-sectional shape of the mask pattern 31 is polygonal or arcuate.

[0037] The cross section of the mask pattern 31 refers to a cross section in a direction perpendicular to the substrate 10 .

[0038] For example, Figure 1 As shown, the cross-sectional shape of the mask pattern 31 is a triangle. The tip of the mask pattern 31 faces away from the substrate 10, so that in the process of growing the GaN epitaxial layer, the GaN material is more likely to adhere to the tip of the mask pattern 31 and start to expand laterally from the edge of the graphene layer 30, so as to achieve the purpose of lateral epitaxy, which can effectively reduce the dislocation density of the GaN epitaxial layer, thereby forming a GaN epitaxial layer with better crystal quality above the graphene layer 30.

[0039] For example, the cross-sectional shape of the mask pattern 31 may be semicircular, and the arc surface of the semicircle faces away from the substrate 10. In the process of growing the GaN epitaxial layer, the GaN material is more likely to adhere to the arc surface of the semicircular mask pattern 31 and expand laterally from the edge of the graphene layer 30, thereby achieving the purpose of lateral epitaxy.

[0040] Exemplarily, the cross-sectional shape of the mask pattern 31 may be a trapezoid. And the short side of the trapezoid faces the opposite direction away from the substrate 10. For example, the mask pattern 31 may be a truncated cone structure. In this way, during the growth of the GaN epitaxial layer, the GaN material can be better attached to the end surface of the truncated cone structure to obtain a good GaN base layer 40; this is conducive to allowing the GaN material to expand laterally from the edge of the graphene layer 30 in the subsequent growth process to achieve lateral epitaxy.

[0041] As an example, when the cross-sectional shape of the mask pattern 31 is a trapezoid, the short side length of the trapezoid may be 1 μm to 10 μm. The short side length of the trapezoid is controlled within the above range to ensure that the area of ​​the end face of the mask pattern 31 is large enough to deposit enough GaN material, which is conducive to the attachment of the GaN material to the end face of the truncated cone structure.

[0042] Figure 2 FIG. 1 is a partial schematic diagram of a growth substrate provided by an embodiment of the present disclosure. Figure 2 As shown, the height H of the mask pattern 31 is 5 nm to 15 nm.

[0043] By controlling the height and width of the mask pattern 31 within the above range, the size of the mask pattern 31 can be large enough so that when depositing the GaN material, the GaN material can first adhere to the surface of the mask pattern 31, and will not fall into the recessed area between the mask patterns 31. This is beneficial for the subsequent growth of the GaN material, and the GaN material can grow laterally based on the surface of the mask pattern 31, thereby achieving the purpose of lateral epitaxy.

[0044] Exemplarily, the height of the mask pattern 31 is 10 nm.

[0045] Alternatively, if Figure 2 As shown, the interval L between adjacent mask patterns 31 is 10 μm to 50 μm.

[0046] By controlling the spacing between adjacent mask patterns 31 within the above range, it is ensured that a sufficiently large area of ​​the graphene layer 30 is recessed downward, so that the distance between the GaN material grown in the recess and the boron nitride layer 20 is closer, thereby enhancing the van der Waals force between the substrate 10 and the GaN epitaxial layer, and effectively alleviating the lattice mismatch and thermal mismatch between the epitaxial layer and the substrate 10.

[0047] Exemplarily, the interval between adjacent mask patterns 31 is 30 μm.

[0048] In one implementation of the present disclosure, Figure 1 As shown, the recessed areas between the mask patterns 31 on the graphene layer 30 expose the boron nitride layer 20 , that is, the recessed areas penetrate the graphene layer 30 .

[0049] In this implementation, the GaN material grown in the recess can directly contact the boron nitride layer 20, which can enhance the van der Waals force between the boron nitride layer 20 and the GaN material, allowing the GaN epitaxial layer to be more firmly fixed on the growth substrate.

[0050] In another implementation of the present disclosure, the depth of the concave hole is less than the thickness of the graphene layer 30, and the thickness of the graphene layer 30 in the concave hole is less than or equal to 0.7 nm.

[0051] In this implementation, the GaN material grown in the depression does not directly contact the boron nitride layer 20, that is, the depression area does not penetrate the graphene layer 30. At the same time, the thickness of the graphene layer 30 is controlled to be small enough, so that the boron nitride layer 20 can still exert van der Waals force on the GaN material.

[0052] Since the graphene layer 30 is not etched through, that is, the GaN material is not attached to the boron nitride layer 20, when the substrate 10 and the epitaxial layer are separated by mechanical peeling, the GaN material will not be torn during the peeling process to affect the GaN epitaxial layer.

[0053] Optionally, the thickness of the boron nitride layer 20 is 1 nm to 3 nm.

[0054] By controlling the thickness of the boron nitride layer 20 within the above range, the thickness of the boron nitride layer 20 can be ensured to be large enough, so that the boron nitride layer 20 exerts a sufficiently large van der Waals force on the GaN material, so that the GaN epitaxial layer can be more securely fixed on the growth substrate.

[0055] Exemplarily, the thickness of the boron nitride layer 20 is 2 nm.

[0056] Alternatively, if Figure 1 As shown, the growth substrate further includes a GaN foundation layer 40 , and the GaN foundation layer 40 is located on the surface of the graphene layer 30 having the mask pattern 31 .

[0057] Before growing the GaN epitaxial layer, a good quality GaN base layer 40 is first formed on the surface of the graphene layer 30, so that the GaN epitaxial layer subsequently grown on the GaN base layer 40 maintains good crystal quality, thereby improving the quality of the prepared GaN epitaxial layer.

[0058] Figure 3 FIG. 1 is a flow chart of a method for preparing a growth substrate provided by an embodiment of the present disclosure. Figure 3 As shown, the preparation method comprises:

[0059] Step S11: providing a substrate.

[0060] Alternatively, the substrate 10 may be a sapphire substrate, a silicon substrate, polycrystalline diamond, Cu foil, and glass.

[0061] Exemplarily, the substrate is a sapphire substrate. The sapphire substrate has a relatively high light transmittance, that is, the substrate is a transparent substrate. In addition, the sapphire material is relatively hard and has relatively stable chemical properties, so that the HEMT epitaxial wafer has good stability.

[0062] In the embodiment of the present disclosure, before growing the boron nitride layer, the process may further include:

[0063] First, place the substrate in a MOCVD (Metal-organic Chemical Vapor Deposition) device, set the reaction chamber pressure to 50 torr to 100 torr, introduce hydrogen, and heat to 1000° C. to 1100° C., and bake the substrate for 5 to 15 minutes to remove contamination on the substrate surface.

[0064] Then, in a hydrogen atmosphere, ammonia is introduced for 1 to 10 minutes to perform a nitridation treatment on the surface of the substrate 10, thereby improving the surface of the substrate 10 and improving the quality of subsequent epitaxial layer growth.

[0065] Step S12 : forming a boron nitride layer 20 on the substrate 10 .

[0066] Specifically, the process may include controlling the pressure in the reaction chamber to be 50 torr to 100 torr, controlling the temperature in the reaction chamber to be 1000° C. to 1100° C., introducing ammonia gas and a boron source into the reaction chamber, adjusting the molar ratio of ammonia gas to the boron source to be 1500 to 1600, and growing the boron nitride layer 20 .

[0067] Exemplarily, the thickness of the grown boron nitride layer 20 is 1 nm to 3 nm. The thickness of the boron nitride layer 20 is within the above range, which can ensure that the thickness of the boron nitride layer 20 is large enough, so that the boron nitride layer 20 exerts a sufficiently large van der Waals force on the GaN material, so that the GaN epitaxial layer can be more securely fixed on the growth substrate.

[0068] Exemplarily, the thickness of the boron nitride layer 20 is 2 nm.

[0069] Step S13 : forming a graphene layer 30 on the boron nitride layer 20 .

[0070] Figure 4 is a diagram showing the preparation state of a growth substrate provided by an embodiment of the present disclosure. Figure 4As shown, the surface of the graphene layer 30 away from the substrate 10 has a plurality of mask patterns 31 arranged at intervals.

[0071] Specifically, the method may include placing the composite substrate 10 obtained by MOCVD in a PECVD (Plasma Enhanced Chemical Vapor Deposition) device to perform a deposition reaction to obtain a graphene layer 30 , and then pattern-etching the graphene layer 30 using processes such as photolithography and etching to form a plurality of mask patterns 31 arranged at intervals on the surface of the graphene layer 30 .

[0072] Alternatively, if Figure 4 As shown, the cross-sectional shape of the mask pattern 31 is polygonal or arcuate.

[0073] The cross section of the mask pattern 31 refers to a cross section in a direction perpendicular to the substrate 10 .

[0074] For example, Figure 1 As shown, the cross-sectional shape of the mask pattern 31 is a triangle, and the tip of the mask pattern 31 faces away from the substrate 10 .

[0075] For example, the cross-sectional shape of the mask pattern 31 may be a semicircle, and the arc surface of the semicircle faces a direction away from the substrate 10 .

[0076] For example, the cross-sectional shape of the mask pattern 31 may be a trapezoid, and the short side of the trapezoid faces away from the substrate 10. For example, the mask pattern 31 may be a truncated cone structure.

[0077] As an example, when the cross-sectional shape of the mask pattern 31 is a trapezoid, the short side length of the trapezoid may be 1 μm to 10 μm. The short side length of the trapezoid is controlled within the above range to ensure that the area of ​​the end face of the mask pattern 31 is large enough to deposit enough GaN material, which is conducive to the attachment of the GaN material to the end face of the truncated cone structure.

[0078] Optionally, the height of the mask pattern 31 is 5 nm to 15 nm, and the interval between adjacent mask patterns 31 is 10 μm to 50 μm.

[0079] After step S13, the following steps are also included:

[0080] First, using the MOCVD process, 15 sccm to 20 sccm of Ga source and 20 slm to 30 slm of ammonia are introduced into the reaction chamber, the temperature in the reaction chamber is controlled to be 900° C. to 950° C., and a GaN film is formed on the surface of the mask pattern 31 .

[0081] Then, 40 sccm to 45 sccm of Ga source and 100 slm to 110 slm of ammonia are introduced into the reaction chamber, and the temperature in the reaction chamber is controlled to be 1070°C to 1100°C, so that the GaN film attached to the surface of the mask pattern 31 grows laterally to form a GaN base layer 40 covering each mask pattern 31.

[0082] In this way, GaN material is first attached to the surface of the mask pattern 31 to obtain a GaN film, and then, on the basis of the GaN film, GaN material continues to grow, so that the GaN material can expand laterally from the edge of the graphene layer 30 to achieve lateral epitaxy, which can effectively reduce the dislocation density of the GaN epitaxial layer, thereby forming a GaN epitaxial layer with better crystal quality above the graphene layer 30.

[0083] The method for preparing a growth substrate provided by the embodiment of the present disclosure uses a two-dimensional material boron nitride layer 20 as an insertion layer. Since the two-dimensional material layers are bonded to each other by van der Waals forces, a plurality of mask patterns 31 arranged at intervals are also provided on the graphene layer 30, so that the GaN epitaxial layer subsequently formed on the graphene layer 30 can be deposited in the gaps between the mask patterns 31. Due to the presence of the graphene / boron nitride composite insertion layer, the lattice mismatch and thermal mismatch between the epitaxial layer and the substrate can be effectively alleviated, the crystal quality of the epitaxial layer can be improved, the film stress of the epitaxial layer can be reduced, and the warping problem of large-size wafers can be solved. In addition, due to the presence of the two-dimensional material boron nitride layer 20, the separation between the substrate 10 and the epitaxial layer can be achieved by simple mechanical peeling, and the substrate 10 can be reused, which is conducive to reducing production costs.

[0084] At the same time, the GaN epitaxial layer grown on the graphene layer 30 will first adhere to the surface of the mask pattern 31; and, during the continuous growth process, the GaN material attached to the surface of the mask pattern 31 will begin to expand laterally from the edge of the graphene layer 30, and eventually cover the surface of the graphene layer 30. This lateral epitaxial growth method can avoid the crystal defects under the graphene layer 30, effectively reduce the dislocation density of the GaN epitaxial layer, and thus form a GaN epitaxial layer with better crystal quality above the graphene layer 30. The growth substrate provided by the embodiment of the present disclosure adopts an organic combination of van der Waals epitaxy and lateral epitaxy, which can not only realize the epitaxy of high-quality single-crystal GaN epitaxial layer on the substrate 10, but also realize the recycling of the substrate 10, thereby reducing the production cost of the enterprise.

[0085] Figure 5 It is a hierarchical schematic diagram of a transistor provided in an embodiment of the present disclosure. Figure 5 The transistor shown is a HEMT epitaxial wafer. Figure 5As shown, the HEMT epitaxial wafer includes the growth substrate and epitaxial layer as described above, and the epitaxial layer includes a GaN high resistance layer 51, a GaN channel layer 52, an AlN insertion layer 53, an AlGaN barrier layer 54 and a GaN cap layer 55 stacked in sequence on the growth substrate.

[0086] In the embodiment of the present disclosure, the preparation process of the above-mentioned film layers on the growth substrate is as follows:

[0087] In the first step, the temperature is set to 1020°C to 1090°C and maintained at a constant temperature, trimethylgallium gas is introduced at a flow rate of 450sccm to 550sccm, ammonia gas is introduced at a flow rate of 30slm to 40slm, and C3H8 is introduced at a flow rate of 750sccm to 900sccm, and the growth is carried out for 14min to 15min, thereby forming a GaN high resistance layer 51 with a thickness of 1200nm to 1500nm on the GaN base layer 40.

[0088] In the second step, the temperature is set to 1020°C to 1090°C, the pressure in the reaction chamber is increased to 150 torr, and trimethylgallium gas is introduced at a flow rate of 200sccm to 300sccm and ammonia gas is introduced at a flow rate of 55slm to 65slm. The growth is carried out for 5min to 7min, thereby forming a GaN channel layer 52 with a thickness of 250nm to 300nm on the GaN high resistance layer 51.

[0089] The third step is to set the temperature to 980°C to 1050°C and maintain a constant temperature, while introducing trimethylaluminum gas at a flow rate of 35sccm to 40sccm and ammonia gas at a flow rate of 10slm to 12slm, and grow for 1 minute to form an AlN insertion layer 53 with a thickness of 1nm to 2nm on the GaN channel layer 52.

[0090] In the fourth step, the temperature is set to 980°C to 1050°C, and trimethylaluminum gas is introduced at a flow rate of 35sccm to 40sccm, trimethylgallium gas is introduced at a flow rate of 25sccm to 30sccm, and ammonia gas is introduced at a flow rate of 10slm to 12slm. The growth is carried out for 5 minutes to form a 20nm thick AlGaN barrier layer 54 on the AlN insertion layer 53.

[0091] In the fifth step, the temperature is set to 980°C to 1050°C and maintained constant, while introducing ammonia gas at a flow rate of 10slm to 12slm and trimethylgallium gas at a flow rate of 25sccm to 30sccm, and growing for 30s to form a 1nm to 2nm thick GaN cap layer 55 on the AlGaN barrier layer 54.

[0092] The above description is only an optional embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A growth substrate, characterized in that: The growth substrate comprises: a substrate (10), a boron nitride layer (20) and a graphene layer (30); the boron nitride layer (20) and the graphene layer (30) are sequentially stacked on the substrate (10); and a surface of the graphene layer (30) away from the substrate (10) has a plurality of mask patterns (31) arranged at intervals.

2. The growth substrate according to claim 1, characterized in that The cross-sectional shape of the mask pattern (31) is polygonal or arcuate.

3. The growth substrate according to claim 1, characterized in that The height (H) of the mask pattern (31) is 5 nm to 15 nm.

4. The growth substrate according to claim 1, characterized in that The distance (L) between adjacent mask patterns (31) is 10 μm to 50 μm.

5. The growth substrate according to claim 1, characterized in that The thickness of the boron nitride layer (20) is 1 nm to 3 nm.

6. The growth substrate according to any one of claims 1 to 5, characterized in that: The growth substrate further comprises a GaN base layer (40), and the GaN base layer (40) is located on the surface of the graphene layer (30) having the mask pattern (31).

7. A method for preparing a growth substrate, characterized in that: The preparation method comprises: Providing a substrate (10); forming a boron nitride layer (20) on the substrate (10); A graphene layer (30) is formed on the boron nitride layer (20), and a surface of the graphene layer (30) away from the substrate (10) has a plurality of mask patterns (31) arranged at intervals.

8. The preparation method according to claim 7, characterized in that: Forming a boron nitride layer (20) on the substrate (10) comprises: The pressure of the reaction chamber is controlled to be 50 torr to 100 torr, the temperature in the reaction chamber is controlled to be 1000° C. to 1100° C., ammonia and a boron source are introduced into the reaction chamber, and the molar ratio of ammonia to the boron source is adjusted to be 1500 to 1600 to grow the boron nitride layer (20).

9. The preparation method according to claim 7, characterized in that: After forming a graphene layer (30) on the boron nitride layer (20), the method further comprises: Introducing 15 sccm to 20 sccm of Ga source and 20 slm to 30 slm of ammonia into the reaction chamber, controlling the temperature in the reaction chamber to 900° C. to 950° C., and forming a GaN film on the surface of the mask pattern (31); 40 sccm to 45 sccm of Ga source and 100 slm to 110 slm of ammonia are introduced into the reaction chamber, and the temperature in the reaction chamber is controlled to be 1070° C. to 1100° C., so that the GaN film attached to the surface of the mask pattern (31) grows laterally, forming a GaN base layer (40) covering each of the mask patterns (31).

10. A transistor, characterized in that: The transistor comprises a growth substrate and an epitaxial layer as claimed in any one of claims 1 to 6, wherein the epitaxial layer comprises a GaN high resistance layer (51), a GaN channel layer (52), an AlN insertion layer (53), an AlGaN barrier layer (54) and a GaN cap layer (55) sequentially stacked on the growth substrate.

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