Material structure and epitaxial method of gallium nitride schottky diode

Abstract

This invention discloses a material structure and epitaxial method for a gallium nitride Schottky diode, comprising, in the epitaxial order: a substrate; an aluminum nitride (AlN) nucleation layer; a lower aluminum gallium nitride (AlGaN) stress modulation layer; an unintentionally doped (Uid) GaN buffer layer; and an upper AlGaN stress modulation layer; n + -Heavy GaN layer; n ++ -GaN ohmic highly doped layer; n-GaN transition layer; n ‑ -GaN lightly doped layer. Based on the metal-organic chemical vapor deposition (MOCVD) method, a stress modulation layer of AlGaN underlayer is introduced at the interface between the AlN nucleation layer and the UidGaN buffer layer to reduce thermal mismatch stress; and a stress modulation layer of AlGaN underlayer is introduced at the interface between the UidGaN buffer layer and the n + - The GaN heavily doped layer interface introduces a stress modulation layer on top of AlGaN to reduce lattice mismatch stress; in n ++ -GaN ohmic highly doped layer and n ‑ An n-GaN transition layer is introduced between the lightly doped GaN layers, and n ‑ - The GaN lightly doped layer is produced using a high-temperature, low-growth-rate process to improve n ‑ - Quality and electronic transport properties of lightly doped GaN layers. The GaN SBD epitaxial material achieved by this method has high quality, low stress, and low sheet resistance, which is beneficial to improving the performance of GaN SBD devices.

Description

Technical Field

[0001] This invention relates to the material structure and epitaxial method of a gallium nitride Schottky diode, belonging to the field of semiconductor epitaxial material technology. Background Technology

[0002] To realize the practical application of terahertz technology, the first step is to develop a terahertz power source circuit. Currently, the most likely approach to achieving this is to utilize the SBD (Self-Dual-Band) frequency doubling principle to develop terahertz circuits above 600 GHz. Compared to second-generation semiconductors such as gallium arsenide (GaAs) and indium phosphide (InP), GaN materials possess characteristics such as a wide bandgap, high breakdown voltage, and high electron saturation velocity. Therefore, GaN SBD devices can achieve higher output power at high frequencies and are considered one of the ideal solutions for terahertz applications. However, currently developed GaN SBD devices suffer from high series resistance, resulting in low cutoff frequency and operating efficiency, which cannot meet the requirements of terahertz applications.

[0003] Currently, there are two main methods to reduce the series resistance of GaN SBD devices: one is to introduce a heterojunction multi-channel structure, which increases the two-dimensional electron gas density by using multiple heterojunction channels, thereby reducing the series resistance. However, this method has the drawbacks of complex structure, difficult fabrication, and the mutual coupling effect of multiple channels limiting the full realization of device performance; the other is to increase n + -GaN heavily doped layer, n ++ The high doping concentration of GaN ohmic layers increases the electron density per unit area, reduces the sheet resistance of GaNSBD epitaxial materials, thereby reducing the series resistance of devices and increasing tunneling current.

[0004] Silane is a commonly used n-type doping source in GaN materials due to its low cost and high incorporation efficiency. However, the significant difference in atomic radius between silicon and gallium leads to substantial lattice mismatch and thermal mismatch stress in GaN materials when doped with high doses of silicon. This results in high stress and a high crystal defect density in the epitaxial material. Furthermore, the stress increases with doping concentration and thickness, eventually causing numerous cracks on the epitaxial surface, severely impacting material quality. To maintain low stress and high quality in GaN SBD epitaxial materials, it is necessary to reduce the doping concentration and thickness, i.e., increase the sheet resistance. However, this results in excessively high series resistance in GaN SBD devices, failing to meet the requirements for terahertz power source circuits. Therefore, effectively controlling epitaxial stress and maintaining high material quality while significantly reducing the sheet resistance of GaN SBD epitaxial materials, thereby substantially reducing the series resistance of GaN SBD devices, is of great significance for the realization and application of terahertz GaN SBD power source circuits. Summary of the Invention

[0005] Current GaN SBD technology is limited by the high stress and low quality of epitaxial materials, resulting in high sheet resistance and poor electronic transport characteristics. This leads to high series resistance, low cutoff frequency and low operating efficiency, which cannot meet the development requirements of terahertz power source circuits.

[0006] To address the problems of existing technologies, the present invention aims to propose a material structure and epitaxial method for gallium nitride Schottky diodes, by introducing Al at the interface between the AlN nucleation layer and the UidGaN buffer layer. x Ga 1-x The N-layer stress modulation layer reduces the thermal mismatch stress between the substrate and the GaN SBD epitaxial material; the UidGaN buffer layer and the n-layer... + -GaN heavy doping interface introduces Al y Ga 1-y N-layer stress modulation layer, reducing the stress difference between uidGaN buffer layer and n + - Interlayer lattice mismatch stress in heavily doped GaN; in n ++ -GaN ohmic high-doped layer and n - - An n-GaN transition layer is introduced between lightly doped GaN layers, and n-GaN is grown using a high-temperature, low-growth-rate process. - -Light GaN doping layer, improves n - - Material quality and electronic transport properties of lightly doped GaN layers. The GaN SBD epitaxial material achieved by this method has high quality, low stress, and low sheet resistance, which is beneficial for reducing the series resistance of GaN SBD devices, improving the cutoff frequency and operating efficiency of the devices, and realizing the development of GaN terahertz power source circuits.

[0007] To address the problems in the existing technology, the technical solution adopted by this invention is as follows:

[0008] A material structure for a gallium nitride Schottky diode, wherein the material structure comprises, from bottom to top, a substrate, an AlN nucleation layer, and an Al... x Ga 1-x N-layer stress modulation layer, UidGaN buffer layer, Al y Ga 1-y N upper stress modulation layer, n + -GaN heavily doped layer, n ++ -GaN ohmic highly doped layer, n-GaN transition layer, n - It consists of a lightly doped GaN layer.

[0009] As an improvement, the Al x Ga 1-x The thickness D1 of the N-layer stress modulation layer is 10-40 nm, and x is 10-40%. Al y Ga1-y The thickness D2 of the stress modulation layer on top of N is 5-30 nm, and y is 10-35%. Here, x represents the alloying percentage of Al in the AlGaN alloy within the corresponding layer, and y represents the alloying percentage of Al. (Introduction of Al...) y Ga 1-y The N-layer stress modulation layer can improve the relationship between the uidGaN buffer layer and n. + -Heavy doping of GaN reduces interlayer lattice mismatch stress and material warpage. When Al y Ga 1-y When the upper stress modulation layer of N is thick (D2 > 30 nm) and the aluminum content is high (y > 35%), Al y Ga 1-y The lattice constant of the upper stress modulation layer N is lower than that of n. + - The lattice constant of the heavily doped GaN layer leads to the relationship between the uidGaN buffer layer and n + -Heavily doped GaN exhibits increased interlayer lattice mismatch stress, which is detrimental to subsequent n-layer remodeling. + -For high-quality epitaxial growth of heavily doped GaN layers, the D2 range of the upper stress modulation layer should be 5-30 nm, and the Al composition y range should be 10-35%.

[0010] As an improvement, an n-GaN transition layer with a thickness D4 ranging from 3 to 15 nm is used.

[0011] As an improvement, n + -Heavy GaN doped layer, where the product of doping thickness and doping concentration is ≥2.7*10⁻⁶. 15 cm -2 The corresponding sheet resistance is ≤12Ω / □. This is achieved by introducing Al... x Ga 1-x The N-layer stress modulation layer reduces thermal mismatch stress and introduces Al. y Ga 1-y The N-layer stress modulation layer reduces lattice mismatch stress, thus controlling the stress in GaN SBD epitaxial materials at a low level. This means that while maintaining high material quality and a relatively smooth surface morphology, the N-layer... + The product of the doping thickness and doping concentration in heavily doped GaN layers is improved, resulting in a corresponding decrease in sheet resistance. To achieve lower series resistance in GaN SBD devices, n + - The product of the GaN heavily doped layer thickness and doping concentration is ≥ 2.7 * 10⁻⁶. 15 cm -2 The corresponding sheet resistance is ≤12Ω / □.

[0012] As an improvement, n ++ The thickness D3 of the GaN ohmic highly doped layer ranges from 50 to 200 nm, and the doping concentration is ≥5*10⁻⁶. 19 cm -3Furthermore, an indium source is introduced during the growth process. To reduce the difficulty of ohmic contact fabrication in GaN SBD devices and achieve high-quality ohmic contact characteristics, the thickness of the highly doped ohmic layer D3 is ≥ 50 nm, and the doping concentration is ≥ 5*10⁻⁶. 19 cm -3 Meanwhile, in order to maintain a good surface morphology of the ohmic highly doped layer, for subsequent n... - GaN lightly doped layer growth provides a higher quality substrate, while ohmic highly doped layer thickness D3 ≤ 200 nm. ++ Introducing an indium surfactant source during the growth of a highly doped GaN ohmic layer can improve material quality and surface morphology.

[0013] The epitaxial method for the material structure of a gallium nitride Schottky diode, as described above, includes the following steps:

[0014] (1) Select a substrate and place it on the base of the equipment such as MOCVD vapor phase epitaxial growth. Fill the reaction chamber with hydrogen gas, set the reaction chamber pressure to 30-150 torr, and simultaneously raise the temperature to 1000-1100℃ to ensure that the substrate is baked in a hydrogen atmosphere for 5-15 minutes to remove contaminants from the substrate surface.

[0015] (2) Under an ammonia atmosphere, the reaction chamber is heated to 1100-1250℃, the pressure is set to 30-200 torr, an aluminum source is introduced, and an AlN nucleation layer of 15-50 nm thickness is grown. The aluminum source is then turned off.

[0016] (3) Under an ammonia atmosphere, the reaction chamber temperature was set to 980-1120℃ and the pressure to 50-250 torr. Gallium and aluminum sources were introduced to grow an Al layer with a thickness of D1. x Ga 1-x The N-layer is a stress modulation layer, where x is the Al composition of the AlGaN alloy, and the gallium and aluminum sources are turned off; Al is introduced. x Ga 1-x The N-layer stress modulation layer can improve the thermal mismatch stress between the substrate and the GaN SBD epitaxial material, and reduce the warpage of the epitaxial material; when Al x Ga 1-x When the lower stress modulation layer is thick (D1 > 40 nm) and the aluminum content is high (x > 40%), the GaN lateral epitaxial growth mode is suppressed, resulting in the degradation of epitaxial material quality and a reduced effect on improving thermal mismatch stress. Therefore, the thickness D1 of the lower stress modulation layer is 10-40 nm and the Al content x ranges from 10-40%.

[0017] (4) Set the reaction chamber temperature to 950-1100℃ and the pressure to 100-500 torr under an ammonia atmosphere, introduce the gallium source, grow a 0.5-1.5μm thick UidGaN buffer layer, and then turn off the gallium source;

[0018] (5) Under an ammonia atmosphere, set the reaction chamber temperature to 950-1100℃ and the pressure to 50-250 torr, introduce gallium and aluminum sources, and grow an Al layer with a thickness of D2. y Ga 1-y N is an upper stress modulation layer, where y is the Al composition of the AlGaN alloy, and the gallium source and aluminum source are turned off;

[0019] (6) Under an ammonia atmosphere, set the reaction chamber temperature to 950-1100℃ and the pressure to 100-500 torr, introduce gallium source and silane, and grow n + -Heavy GaN doped layer, with gallium source and silane turned off;

[0020] (7) Maintaining constant temperature and pressure in the reaction chamber under an ammonia atmosphere, introduce gallium source, indium source, and silane to grow an n-thickness layer with a thickness of D3. ++ -GaN ohmic highly doped layer;

[0021] (8) Keeping the growth conditions unchanged, grow an n-GaN transition layer with a thickness of D4. During the growth of the n-GaN transition layer, the silane flow rate is gradually reduced to n. ++ -The silane flux of the GaN ohmic highly doped layer is 1 / 100 to 1 / 10, and then the gallium source, indium source and silane are turned off;

[0022] (9) Maintaining a constant pressure in the reaction chamber under an ammonia atmosphere, the temperature is increased by 20-60℃ on the basis of the n-GaN transition layer, and a gallium source and silane are introduced. n-GaN is then grown at a growth rate of V. - - Lightly doped GaN layer, gallium source and silane shut off; cooled to room temperature, epitaxial wafer removed. The high-temperature, low-rate growth process improves n... - - The material quality and electron mobility of the lightly doped GaN layer are beneficial to improving the performance of GaN SBD devices. That is, the epitaxial method is completed in an ammonia atmosphere from step (2) to the end of the reaction.

[0023] The improvement is that the substrate in step (1) is a SiC single crystal substrate, a silicon substrate, or a sapphire substrate.

[0024] The improvement is that the growth rate V in step (9) ranges from 0.3 to 1.5 μm / hour.

[0025] Beneficial effects:

[0026] Compared with the prior art, the material structure and epitaxial method of the gallium nitride Schottky diode of the present invention have the following advantages:

[0027] (1) By introducing Al at the interface between the AlN nucleation layer and the UidGaN buffer layer x Ga 1-xThe N-layer stress modulation layer reduces the thermal mismatch stress between the substrate and the GaN SBD epitaxial material; the UidGaN buffer layer and the n-layer... + -GaN heavy doping interface introduces Al y Ga 1-y N-layer stress modulation layer, reducing the stress difference between uidGaN buffer layer and n + The interlayer lattice mismatch stress in heavily doped GaN significantly improves the stress of GaN SBD epitaxial materials, resulting in a substantial reduction in warpage. Thanks to this stress reduction, GaN SBD epitaxial materials maintain high material quality and a relatively smooth surface morphology. + The product of the doping thickness and doping concentration of the heavily doped GaN layer is improved, which helps to reduce the low series resistance of GaN SBD devices and improve high-frequency performance.

[0028] (2) In n ++ -GaN ohmic high-doped layer and n - - An n-GaN transition layer is introduced between lightly doped GaN layers, and n-GaN is grown using a high-temperature, low-growth-rate process. - -Light GaN doping layer, improves n - The material quality and electronic transport properties of lightly doped GaN layers further enhance the performance of GaN SBD devices. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the GaN SBD material structure grown in Example 1;

[0030] Figure 2 This is a schematic diagram of the structure of the GaN SBD material grown in Comparative Example 1;

[0031] Figure 3 (a) is a surface morphology image of the 4-inch GaN SBD epitaxial material of Example 1.

[0032] Figure 3 (b) Surface morphology of the 4-inch GaN SBD epitaxial material grown in Comparative Example 1 (tested by atomic force microscopy, test range 5μm×5μm);

[0033] Figure 4 (a) is a distribution diagram of the 4-inch GaN SBD epitaxial material sheet resistor wafer grown in Example 1;

[0034] Figure 4 (b) is a distribution diagram of the sheet resistor material of the 4-inch GaN SBD epitaxial material grown in Comparative Example 1. Detailed Implementation

[0035] The technical solution of the present invention will be described in detail below, but the scope of protection of the present invention includes, but is not limited to, the embodiments described.

[0036] Example 1

[0037] like Figure 1 As shown, the material structure of a gallium nitride Schottky diode (GaN SBD material structure) consists of, from bottom to top, a substrate, an AlN nucleation layer, a lower AlGaN stress modulation layer, a UidGaN buffer layer, an upper AlGaN stress modulation layer, and an n... + -GaN heavily doped layer, n ++ -GaN ohmic highly doped layer, n-GaN transition layer, n - -GaN lightly doped layer.

[0038] Its extensional method includes the following steps:

[0039] (1) Select a 4-inch SiC substrate and place it on the base inside the MOCVD material growth equipment;

[0040] (2) The reaction chamber is heated to 1070°C and the pressure is set to 100 torr. The substrate is baked for 10 minutes in a hydrogen atmosphere to remove contaminants from the substrate surface.

[0041] (3) In an ammonia atmosphere, the reaction chamber was heated to 1150℃, the pressure was set to 80 torr, trimethylaluminum was introduced, a 30nm thick AlN nucleation layer was grown, and the trimethylaluminum was turned off.

[0042] (4) Under an ammonia atmosphere, the reaction chamber temperature was set to 1080℃ and the pressure to 100 torr. Trimethylgallium and trimethylaluminum were introduced to grow a 20nm thick Al layer. 0.2 Ga 0.8 N-layer stress modulation layer, shutting off trimethylgallium and trimethylaluminum;

[0043] (5) Set the reaction chamber temperature to 1060℃ and the pressure to 250 torr under an ammonia atmosphere, introduce trimethylgallium, grow a 1.0μm thick UidGaN buffer layer, and then turn off the trimethylgallium.

[0044] (6) Under an ammonia atmosphere, the reaction chamber temperature was set to 1060℃ and the pressure to 120 torr. Trimethylgallium and trimethylaluminium were introduced to grow a 15nm thick Al layer. 0.15 Ga 0.85 N upper stress modulation layer, turn off trimethylgallium and trimethylaluminum;

[0045] (7) Under an ammonia atmosphere, the reaction chamber temperature was set to 1060℃ and the pressure to 200 torr. Trimethylgallium and silane were introduced to grow a 1.5μm thick material with a doping concentration of 2.0*10⁻⁶. 19cm -3 n + -Heavy GaN doped layer (the product of doping thickness and doping concentration is 3.0*10⁻⁶) 15 cm -2 ), shut down trimethylgallium and silane;

[0046] (8) Under an ammonia atmosphere, maintaining constant temperature and pressure in the reaction chamber, trimethylgallium (250 sccm), trimethylindium (200 sccm), and silane (6.8 sccm) are introduced to grow a 100 nm thick substrate with a doping concentration of 6.0 × 10⁻⁶. 19 cm -3 n ++ -GaN ohmic highly doped layer;

[0047] (9) Keeping the growth conditions unchanged, a 7 nm thick n-GaN transition layer was grown. During the growth of the transition layer, the silane flow rate was gradually reduced from 6.5 sccm to 0.25 sccm, and then trimethylgallium, trimethylindium and silane were turned off.

[0048] (10) Under an ammonia atmosphere, while maintaining a constant pressure in the reaction chamber, the temperature was raised to 1090℃, and trimethylgallium and silane were introduced. A 200 nm thick layer with a doping concentration of 4.0 × 10⁻⁶ was grown at a growth rate of 0.6 μm / hour. 17 cm -3 n - - GaN lightly doped layer, shut down trimethylgallium and silane.

[0049] (11) Under ammonia protection, the epitaxial wafer was removed and cooled to room temperature.

[0050] Comparative Example 1

[0051] A gallium nitride Schottky diode material structure, from bottom to top, consists of a substrate, an AlN nucleation layer, a UidGaN buffer layer, and an n... + -GaN heavily doped layer, n ++ -GaN ohmic highly doped layer, n - - Lightly doped GaN layer. Epitaxial method, including the following steps:

[0052] (1) Select a 4-inch SiC substrate and place it on the base inside the MOCVD material growth equipment;

[0053] (2) The reaction chamber is heated to 1070°C and the pressure is set to 100 torr. The substrate is baked for 10 minutes in a hydrogen atmosphere to remove contaminants from the substrate surface.

[0054] (3) In an ammonia atmosphere, the reaction chamber was heated to 1150℃, the pressure was set to 80 torr, trimethylaluminum was introduced, a 65nm thick AlN nucleation layer was grown, and the trimethylaluminum was turned off.

[0055] (4) Set the reaction chamber temperature to 1060℃ and the pressure to 250 torr under an ammonia atmosphere, introduce trimethylgallium, grow a 1.0μm thick UidGaN buffer layer, and then turn off the trimethylgallium.

[0056] (5) Under an ammonia atmosphere, the reaction chamber temperature was set to 1060℃ and the pressure to 200 torr. Trimethylgallium and silane were introduced to grow a 1.5μm thick material with a doping concentration of 7*10. 18 cm -3 n + -Heavy GaN doped layer (the product of doping thickness and doping concentration is 1.05*10⁻⁶) 15 cm -2 ), shut down trimethylgallium and silane. If n + - The doping concentration of the heavily doped GaN layer exceeds 8*10 18 cm -3 Excessive stress (or warping) in the epitaxial material leads to numerous cracks on the material surface, resulting in material quality degradation.

[0057] (6) Under an ammonia atmosphere, while maintaining constant temperature and pressure in the reaction chamber, trimethylgallium and silane were introduced to grow a 100 nm thick substrate with a doping concentration of 6.0 × 10⁻⁶. 19 cm -3 n ++ -GaN ohmic highly doped layer, shutting off trimethylgallium and silane;

[0058] (7) Under an ammonia atmosphere, while maintaining constant temperature and pressure in the reaction chamber, trimethylgallium and silane were introduced to grow a 200 nm thick substrate with a doping concentration of 4.0 × 10⁻⁶. 17 cm -3 n - - GaN lightly doped layer, shut down trimethylgallium and silane.

[0059] (8) Remove the epitaxial wafer after the ammonia gas has cooled to room temperature.

[0060] The 4-inch GaN SBD epitaxial material grown in Example 1 of this invention has a curvature of +6.9 μm, while the 4-inch GaN SBD epitaxial material grown in Comparative Example 1 has a curvature of -37.8 μm. This indicates that the present invention introduces Al at the interface between the AlN nucleation layer and the UidGaN buffer layer. x Ga 1-x N-layer stress modulation layer, in the UidGaN buffer layer and n + -GaN heavy doping interface introduces Al y Ga 1-y The N-layer stress modulation layer significantly improves the stress of GaN SBD epitaxial materials and reduces material warpage.

[0061] The 4-inch GaN SBD epitaxial material grown in Embodiment 1 of this invention is as follows: Figure 3 As shown in (a), the surface is smooth with no obvious defects, and the surface roughness of 5μm × 5μm is 0.298nm and n - The electron mobility of the lightly doped GaN layer is 550 cm⁻¹. 2 / Vs; However, the 4-inch GaN SBD epitaxial material grown using existing technology has a large surface undulation and contains small-sized pit defects, with a surface roughness of 0.598nm for a 5μm × 5μm surface. Figure 3 As shown in (b), and n - The electron mobility of the lightly doped GaN layer is 420 cm⁻¹. 2 / Vs indicates that the present invention is achieved through n ++ -GaN ohmic high-doped layer and n - - An n-GaN transition layer is introduced between lightly doped GaN layers, and n-GaN is grown using a high-temperature, low-growth-rate process. - -GazN lightly doped layer effectively improves n - - Material quality and electron transport properties of lightly doped GaN layers.

[0062] like Figure 4 (a) Figure 4 As shown in (b), the sheet resistance of the 4-inch GaN SBD epitaxial material grown in Embodiment 1 of the present invention is 10.5 Ω / □, where n + The product of the doping thickness and doping concentration of the heavily doped GaN layer is 3.0 * 10⁻⁶. 15 cm -2 The sheet resistance of the 4-inch GaN SBD epitaxial material grown in Comparative Example 1 is 36.1 Ω / □, where n + The product of the doping thickness and doping concentration of the heavily doped GaN layer is 1.05 * 10⁻⁶. 15 cm -2 This indicates that the present invention improves stress while n + The product of the doping thickness and doping concentration of the heavily doped GaN layer was significantly improved, resulting in a significant decrease in sheet resistance. This is beneficial for reducing the low series resistance of GaN SBD devices and improving high-frequency performance.

[0063] In summary, this invention significantly improves n while maintaining a smooth surface, low stress, and high material quality. + -GaN heavily doped layer, n ++ - The doping concentration of the GaN ohmic highly doped layer, and n -The electron mobility of the lightly doped GaN layer reduces the sheet resistance of the epitaxial material, which helps to reduce the series resistance of GaN SBD devices, improve the cutoff frequency and operating efficiency of the devices, and realize the development of GaN terahertz power source circuits.

[0064] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A material structure for a gallium nitride Schottky diode, characterized in that, The material structure, from bottom to top, consists of a substrate, an AlN nucleation layer, and an Al... x Ga 1-x N-layer stress modulation layer, UidGaN buffer layer, Al y Ga 1-y N upper stress modulation layer, n + -GaN heavily doped layer, n ++ -GaN ohmic highly doped layer, n-GaN transition layer, n - It consists of a lightly doped GaN layer.

2. The material structure of the gallium nitride Schottky diode according to claim 1, characterized in that, The Al x Ga 1-x The thickness D1 of the N-layer stress modulation layer is 10-40 nm, and x is 10-40%. Al y Ga 1-y The thickness D2 of the upper stress modulation layer N is 5-30 nm, and y is 10-35%.

3. The material structure of the gallium nitride Schottky diode according to claim 1, characterized in that, The n-GaN transition layer has a thickness D4 ranging from 3 to 15 nm.

4. The material structure of the gallium nitride Schottky diode according to claim 1, characterized in that, n + -Heavy GaN doped layer, where the product of doping thickness and doping concentration is ≥2.7*10⁻⁶. 15 cm -2 The corresponding sheet resistance is ≤12Ω / □.

5. The material structure of the gallium nitride Schottky diode according to claim 1, characterized in that, n ++ The thickness D3 of the GaN ohmic highly doped layer ranges from 50 to 200 nm, and the doping concentration is ≥5*10⁻⁶. 19 cm -3 Furthermore, an indium source is introduced during the growth process.

6. An epitaxial method based on the material structure of a gallium nitride Schottky diode according to claim 1, characterized in that, Includes the following steps: (1) Select a substrate and place it on the base of the equipment such as MOCVD vapor phase epitaxial growth. Fill the reaction chamber with hydrogen gas, set the reaction chamber pressure to 30-150 torr, and simultaneously raise the temperature to 1000-1100℃ to ensure that the substrate is baked in a hydrogen atmosphere for 5-15 minutes to remove contaminants from the substrate surface. (2) Under an ammonia atmosphere, the reaction chamber is heated to 1100-1250℃, the pressure is set to 30-200 torr, an aluminum source is introduced, and an AlN nucleation layer of 15-50 nm thickness is grown. The aluminum source is then turned off. (3) Under an ammonia atmosphere, the reaction chamber temperature is set to 980-1120℃ and the pressure is set to 50-250 torr. Gallium and aluminum sources are introduced to grow Al with a thickness of D1. x Ga 1-x The N-layer is a stress modulation layer, where x is the Al composition of the AlGaN alloy, and the gallium source and aluminum source are turned off. (4) Set the reaction chamber temperature to 950-1100℃ and the pressure to 100-500 torr under an ammonia atmosphere, introduce the gallium source, grow a 0.5-1.5μm thick UidGaN buffer layer, and then turn off the gallium source; (5) Under an ammonia atmosphere, set the reaction chamber temperature to 950-1100℃ and the pressure to 50-250 torr, introduce gallium and aluminum sources, and grow Al with a thickness of D2. y Ga 1-y N is an upper stress modulation layer, where y is the Al composition of the AlGaN alloy, and the gallium source and aluminum source are turned off; (6) Set the reaction chamber temperature to 950-1100℃ and the pressure to 100-500 torr under an ammonia atmosphere, introduce gallium source and silane, and grow n + -Heavy GaN doped layer, with gallium source and silane turned off; (7) Under an ammonia atmosphere, the temperature and pressure of the reaction chamber are kept constant, and gallium source, indium source and silane are introduced to grow an n-thickness layer with a thickness of D3. ++ -GaN ohmic highly doped layer; (8) Keeping the growth conditions unchanged, grow an n-GaN transition layer with a thickness of D4. During the growth of the n-GaN transition layer, the silane flow rate is gradually reduced to n ++ - 1 / 100 to 1 / 10 of the silane flux of the GaN ohmic highly doped layer, then turn off the gallium source, indium source and silane; (9) Under an ammonia atmosphere, maintain a constant pressure in the reaction chamber, raise the temperature by 20-60°C on the basis of the n-GaN transition layer, introduce gallium source and silane, and grow n-GaN at a growth rate of V. - - Lightly doped GaN layer, turn off gallium source and silane; cool to room temperature, remove epitaxial wafer.

7. The epitaxial method for the material structure of a gallium nitride Schottky diode according to claim 6, characterized in that, In step (1), the substrate is a SiC single crystal substrate, a silicon substrate, or a sapphire substrate.

8. The epitaxial method for the material structure of a gallium nitride Schottky diode according to claim 6, characterized in that, In step (9), the growth rate V ranges from 0.3 to 1.5 μm / hour.

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