Silicon-based AlGaN / GaN HEMT epitaxial structure and growth method thereof

Abstract

The invention discloses a silicon-based AlGaN / GaN HEMT epitaxial structure and a growth method thereof. The silicon-based AlGaN / GaN HEMT epitaxial structure comprises a silicon substrate, an AlN buffer layer, a stepped AlGaN stress release layer, a GaN crystal seed bedding coarsening layer, a GaN epitaxial layer, a first AlN insertion layer, a first C-doped GaN layer, a second AlN insertion layer, a second C-doped GaN layer, a third AlN insertion layer, an undoped GaN channel layer, a fourth AlN insertion layer, an AlGaN barrier layer and a GaN capacitor layer which are sequentially stacked from bottom to top. The first C-doped GaN layer and the second C-doped GaN layer comprise a plurality of C-doped layers and non-doped layers which are alternately stacked, and C elements of the C-doped layers are merged in a delta doping mode. According to the invention, delta doping of the C element in GaN epitaxy is adopted, so that the mismatch of lattice defects is effectively relieved, the GaN epitaxial high-resistance layer with relatively high crystal quality is obtained, and the epitaxial crystal quality better than that of a conventional C-doped GaN layer is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor manufacturing, and in particular to a silicon-based AlGaN / GaN HEMT epitaxial structure and a growth method thereof. Background Art

[0002] To date, silicon (Si) materials account for a large proportion of the semiconductor market and play a major role in the development of semiconductor technology. However, due to the low theoretical limit of Si materials themselves, they cannot meet the current demand for low energy consumption. People have gradually turned their attention to the third-generation wide bandgap semiconductor materials with high thermal conductivity, high electron saturation velocity and high breakdown field strength.

[0003] As a typical third-generation semiconductor power device, GaN-HEMT benefits from the excellent properties of GaN materials such as wide bandgap, high electron saturation drift rate, and high critical breakdown electric field. It has a high-concentration, high-mobility two-dimensional electron gas at the AlGaN / GaN heterojunction, thus having the advantages of high power density, high breakdown voltage, and low on-resistance. Therefore, it is widely used in aerospace, 5G base stations, and new energy vehicles.

[0004] Si-based GaN has a higher cost advantage than SiC substrates and GaN self-supporting substrates. However, due to the large lattice mismatch and thermal mismatch coefficient between Si substrates and GaN, stress mismatch is gradually generated during epitaxy, forming a large number of dislocation groups in epitaxial growth, causing surface anomalies such as cracking of the epitaxial layer, which seriously hinders the electrical performance and reliability of GaN-HEMT under high power density working conditions.

[0005] Therefore, how to effectively reduce the lattice and stress mismatch through the design of the epitaxial structure, thereby reducing the crystal defects of Si-based GaN epitaxial materials, is the key to the application of Si-based GaN-HEMT in the RF and power fields. Summary of the invention

[0006] Purpose of the invention: In view of the above shortcomings, the present invention provides a silicon-based AlGaN / GaN HEMT epitaxial structure and a growth method thereof, which reduces the lattice defects of the epitaxial material by reducing the problem of lattice mismatch caused by doping occupying lattice vacancies.

[0007] Technical solution: To solve the above problems, the present invention adopts a silicon-based AlGaN / GaN HEMT epitaxial structure, including a silicon substrate, an AlN buffer layer, a stepped AlGaN stress release layer, a GaN seed pad roughening layer, a GaN epitaxial layer, a first AlN insertion layer, a first C-doped GaN layer, a second AlN insertion layer, a second C-doped GaN layer, a third AlN insertion layer, an undoped GaN channel layer, a fourth AlN insertion layer, an AlGaN barrier layer, and a GaN capacitor layer stacked in sequence from bottom to top; the first C-doped GaN layer and the second C-doped GaN layer include a plurality of alternately stacked C-doped layers and undoped layers, and the C element of the C-doped layer is incorporated by δ-doping.

[0008] Furthermore, the C-doped layer has a thickness of 2-3 nm, and the non-doped layer has a thickness of 20-50 nm.

[0009] Furthermore, the thickness of the first C element δ-doped GaN layer and the second C element δ-doped GaN layer is 0.5-1 μm.

[0010] The present invention also provides a method for growing the silicon-based AlGaN / GaN HEMT epitaxial structure, comprising the following steps: S1, placing a silicon substrate into a reaction chamber, introducing hydrogen gas, and performing high-temperature surface passivation on the silicon substrate; S2, stop the introduction of hydrogen, introduce trimethylaluminum into the reaction chamber, and pre-spread Al source on the surface of the silicon substrate; S3, introducing ammonia gas into the reaction chamber, and then introducing trimethylaluminum to grow an AlN buffer layer on the silicon substrate; S4, introducing ammonia, trimethylgallium, and trimethylaluminum into the reaction chamber, and growing a stepped AlGaN stress release layer on the AlN buffer layer by adjusting the amount of trimethylaluminum introduced; S5, introducing ammonia and trimethylgallium into the reaction chamber to grow a GaN seed crystal pad roughening layer on the stepped AlGaN stress release layer; S6, continuing to introduce ammonia and trimethylgallium into the reaction chamber to grow a GaN epitaxial layer on the GaN seed crystal roughening layer; S7, introducing ammonia and trimethylaluminum into the reaction chamber to grow a first AlN insertion layer on the GaN epitaxial layer; S8, introducing ammonia, trimethylgallium and ethylene into the reaction chamber, and setting the growth rate to be step growth, growing a first C-doped GaN layer on the basis of the first AlN insertion layer, and the C element is incorporated by δ doping; S9, introducing ammonia and trimethylaluminum into the reaction chamber to grow a second AlN insertion layer on the basis of the first C-doped GaN layer; S10, introducing ammonia, trimethylgallium and ethylene into the reaction chamber, and setting the growth rate to be step growth, growing a second C-doped GaN layer on the basis of the second AlN insertion layer, and the C element is incorporated by δ doping; S11, introducing ammonia and trimethylaluminum into the reaction chamber to grow a third AlN insertion layer on the second C-doped GaN layer; S12, introducing ammonia and trimethylgallium into the reaction chamber to grow an undoped GaN channel layer on the third AlN insertion layer; S13, introducing ammonia gas and trimethylaluminum into the reaction chamber to grow a fourth AlN insertion layer on the undoped GaN channel layer; S14, introducing trimethylgallium and trimethylaluminum into the reaction chamber to grow an AlGaN barrier layer on the fourth AlN insertion layer; S15, introducing ammonia and trimethylgallium into the reaction chamber to grow a GaN capacitor layer on the AlGaN barrier layer.

[0011] Furthermore, in step S3, the reaction chamber temperature is first set to 600°C-700°C and the reaction chamber pressure is 100 mbar to grow a first AlN buffer layer; then the reaction chamber temperature is set to 1000°C-1200°C and the reaction chamber pressure remains unchanged to grow a second AlN buffer layer, and the growth temperature of the first AlN buffer layer is lower than the growth temperature of the second AlN buffer layer.

[0012] Furthermore, in step S4, the reaction chamber temperature is 1200°C, the reaction chamber pressure is 100 mbar, and the amount of trimethylaluminum introduced is gradually reduced to generate a high Al component AlGaN epitaxial layer with an Al component molar content of 50%-70%, a medium Al component AlGaN epitaxial layer with an Al component molar content of 40%-60%, and a low Al component AlGaN epitaxial layer with an Al component molar content of 20%-30%.

[0013] Furthermore, in steps S8 and S10, C element is first introduced by δ-doping to grow a C-doped layer, and then C element doping is interrupted to grow a non-doped layer, and a number of alternatingly stacked C-doped layers and non-doped layers are repeatedly grown to finally obtain a first C-doped GaN layer and a second C-doped GaN layer.

[0014] Furthermore, in steps S8 and S10, the growth rate is divided into three stages, the growth rate in the first stage is 0.8-1.2 μm / h, the growth rate in the second stage is 2-3 μm / h, and the growth rate in the third stage is 3-5 μm / h.

[0015] Furthermore, in steps S8 and S10, the temperature of the reaction chamber is 1100° C., and the pressure of the reaction chamber is 100-200 mbar.

[0016] Furthermore, in steps S7, S9, S11 and S13, the temperature of the reaction chamber is 1100°C and the pressure of the reaction chamber is 100 mbar.

[0017] Beneficial effect: Compared with the prior art, the significant advantage of the present invention is that conventional high-concentration continuous C doping has a strong probability of occupying N vacancies, which easily leads to the formation of lattice defects in GaN epitaxy, and further forms dislocations with the epitaxy, thereby forming epitaxial defects in GaN epitaxy, forming leakage channel problems in power devices. By using δ-doping of C elements in GaN epitaxy, the dislocation of lattice defects is effectively alleviated, a GaN epitaxial high-resistance layer with higher crystal quality is obtained, and better epitaxial crystal quality is obtained than conventional C-doped GaN layers. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The overall structural diagram of the epitaxial wafer prepared by the present invention is shown; Figure 2 The XRD rocking curve diagram of the epitaxial wafer prepared in Example 1-3; Figure 3 This is the TEM (transmission electron microscope) test result of the epitaxial wafer prepared in Example 1. DETAILED DESCRIPTION

[0019] The equipment used for the epitaxial structure growth of the present invention is a metal organic chemical vapor deposition (MOCVD) equipment, the carrier gas of the organic metal source is hydrogen and nitrogen, the organic metal source (Group III source) includes a gallium source and an aluminum source, the carbon source is acetylene (C2H4), the nitrogen source (Group V source) is ammonia (NH3), the gallium source is trimethylgallium (TMGa), and the aluminum source is trimethylaluminum (TMAl).

[0020] Example 1

[0021] A method for growing a silicon-based AlGaN / GaN HEMT epitaxial structure in this embodiment includes the following steps: 1. Place a (111) lightly doped silicon wafer on a graphite tray and then put it into the reaction chamber of the MOCVD system; raise the temperature of the MOCVD reaction chamber to 1100°C, set the reaction chamber pressure to 100 mbar, and set the plate speed to 1000 r / h. Introduce hydrogen to perform high-temperature surface purification on the surface of the silicon substrate 1 for 300 seconds to remove oxygen impurities, open the surface suspended bonds, and make the surface full of activity.

[0022] 2. Stop the introduction of hydrogen, set the reaction chamber temperature to 900° C., the reaction chamber pressure to 50 mbar, introduce trimethylaluminum into the reaction chamber for 10 seconds, and pre-spread Al source on the surface of the silicon substrate 1.

[0023] 3. The reaction chamber temperature is set to 600° C., the reaction chamber pressure is set to 100 mbar, ammonia is introduced for pre-nitridation, and then trimethylaluminum is introduced to grow a first AlN buffer layer 2 on the basis of the silicon substrate 1, with an epitaxial thickness of about 10 nm.

[0024] 4. The reaction chamber temperature is set to 1000° C., the reaction chamber pressure is set to 100 mbar, trimethylaluminum is continuously introduced, and a second AlN buffer layer 3 is grown on the basis of the first AlN buffer layer 2, with an epitaxial thickness of about 100 nm.

[0025] 5. The temperature of the reaction chamber is raised to 1200°C, the pressure of the reaction chamber is set to 100 mbar, ammonia, trimethylgallium and trimethylaluminum are introduced, and a high Al component AlGaN stress release layer 4 with an Al molar content of about 70% and a thickness of about 50 nm is grown on the basis of the second AlN buffer layer 3.

[0026] 6. Maintaining the temperature and pressure of the reaction chamber unchanged, reducing the amount of trimethylaluminum introduced, and growing a medium Al component AlGaN stress release layer 5 with an Al molar content of about 60% on the basis of the high Al component AlGaN stress release layer 4, with a thickness of about 100 nm.

[0027] 7. Maintaining the temperature and pressure of the reaction chamber unchanged, continue to reduce the amount of trimethylaluminum introduced, and grow a low Al component AlGaN stress release layer 6 with an Al molar content of about 30% on the basis of the medium Al component AlGaN stress release layer 5, with a thickness of about 500 nm.

[0028] 8. The temperature of the reaction chamber is lowered to 1100°C, the pressure of the reaction chamber is increased to 600 mbar, the rotation speed of the large disk is set to 600 r / h, ammonia and trimethylgallium are introduced, and a GaN seed crystal bedding roughening layer 7 with a thickness of about 100 nm is grown on the basis of the low Al component AlGaN stress release layer 6.

[0029] 9. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 200 mbar, set the rotation speed of the large plate to 1200 r / h, continue to introduce ammonia and trimethylgallium, and grow a GaN epitaxial layer 8 on the basis of the GaN seed crystal roughening layer 7, with a thickness of about 1000 nm.

[0030] 10. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 100 mbar, introduce ammonia and trimethylaluminum, and grow a first AlN insertion layer 9 on the basis of the GaN epitaxial layer 8 with a thickness of about 10 nm.

[0031] 11. Keep the temperature and pressure of the reaction chamber constant, introduce ammonia, trimethylgallium and ethylene, and set the growth rate in three stages. The growth rate in the first stage is 0.8 μm / h, the growth rate in the second stage is 2 μm / h, and the growth rate in the third stage is 3 μm / h. First, C element is incorporated by δ doping to grow a C doped layer with a thickness of 2 nm, then the C element doping is interrupted to grow a non-doped layer with a thickness of 20 nm, and the above steps are repeated to grow 20 sets of alternating stacked C doped layers and non-doped layers, and the first C doped GaN layer 10 is grown on the basis of the first AlN insertion layer 9.

[0032] 12. Keeping the temperature and pressure of the reaction chamber unchanged, introduce ammonia and trimethylaluminum, and grow a second AlN insertion layer 11 on the basis of the first C-doped GaN layer 10, with a thickness of about 10 nm.

[0033] 13. Keeping the temperature and pressure of the reaction chamber unchanged, introduce ammonia, trimethylgallium and ethylene, and set the growth rate in three stages. The growth rate in the first stage is 0.8 μm / h, the growth rate in the second stage is 2 μm / h, and the growth rate in the third stage is 3 μm / h. First, C element is incorporated by δ doping to grow a C-doped layer with a thickness of 2 nm, and then the C element doping is interrupted to grow a non-doped layer with a thickness of 20 nm. Repeat the above steps to grow 20 groups of alternating stacked C-doped layers and non-doped layers, and grow a second C-doped GaN layer 12 on the basis of the second AlN insertion layer 11.

[0034] 14. Keeping the temperature and pressure of the reaction chamber unchanged, introduce ammonia and trimethylaluminum to grow a third AlN insertion layer 13 on the second C-doped GaN layer 12 with a thickness of about 10 nm.

[0035] 15. Keep the temperature of the reaction chamber unchanged, increase the pressure of the reaction chamber to 200 mbar, stop introducing ethylene, continue to introduce ammonia and trimethylgallium, and grow an undoped GaN channel layer 14 on the third AlN insertion layer 13 with a thickness of about 300 nm.

[0036] 16. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 100 mbar, introduce ammonia and trimethylaluminum, and grow a fourth AlN insertion layer 15 on the undoped GaN channel layer 14 with a thickness of about 10 nm.

[0037] 17. The temperature of the reaction chamber is lowered to 1000° C., the pressure of the reaction chamber is maintained at 100 mbar, trimethylgallium and trimethylaluminum are introduced, and an AlGaN barrier layer 16 with an Al content of about 20% and a thickness of about 20 nm is grown on the fourth AlN insertion layer 15 .

[0038] 18. The temperature of the reaction chamber is raised to 1100° C., the pressure of the reaction chamber is increased to 150 mbar, ammonia and trimethylgallium are introduced, and a GaN capacitor layer 17 is grown on the AlGaN barrier layer 16 with a thickness of about 2 nm.

[0039] The final product is Figure 1 The epitaxial structure shown.

[0040] Example 2

[0041] A method for growing a silicon-based AlGaN / GaN HEMT epitaxial structure in this embodiment includes the following steps: 1. Place a (111) lightly doped silicon wafer on a graphite tray and then put it into the reaction chamber of the MOCVD system; raise the temperature of the MOCVD reaction chamber to 1200°C, set the reaction chamber pressure to 150 mbar, and set the plate speed to 1100 r / h. Introduce hydrogen to perform high-temperature surface purification on the surface of the silicon substrate 1 for 400 seconds to remove oxygen impurities, open the surface floating bonds, and make the surface full of activity.

[0042] 2. Stop the introduction of hydrogen, set the reaction chamber temperature to 950° C., the reaction chamber pressure to 75 mbar, introduce trimethylaluminum into the reaction chamber for 20 seconds, and pre-spread Al source on the surface of the silicon substrate 1.

[0043] 3. The reaction chamber temperature is set to 650° C., the reaction chamber pressure is set to 100 mbar, ammonia is introduced for pre-nitridation, and then trimethylaluminum is introduced to grow a first AlN buffer layer 2 on the basis of the silicon substrate 1, with an epitaxial thickness of about 20 nm.

[0044] 4. The reaction chamber temperature is set to 1100° C., the reaction chamber pressure is set to 100 mbar, trimethylaluminum is continuously introduced, and a second AlN buffer layer 3 is grown on the basis of the first AlN buffer layer 2, with an epitaxial thickness of about 150 nm.

[0045] 5. The temperature of the reaction chamber is raised to 1200° C., the pressure of the reaction chamber is set to 100 mbar, ammonia, trimethylgallium and trimethylaluminum are introduced, and a high Al component AlGaN stress release layer 4 with an Al molar content of about 60% and a thickness of about 75 nm is grown on the basis of the second AlN buffer layer 3.

[0046] 6. Maintaining the temperature and pressure of the reaction chamber unchanged, reducing the amount of trimethylaluminum introduced, and growing a medium Al component AlGaN stress release layer 5 with an Al molar content of about 50% on the basis of the high Al component AlGaN stress release layer 4, with a thickness of about 150 nm.

[0047] 7. Maintaining the temperature and pressure of the reaction chamber unchanged, continue to reduce the amount of trimethylaluminum introduced, and grow a low Al component AlGaN stress release layer 6 with an Al molar content of about 25% on the basis of the medium Al component AlGaN stress release layer 5, with a thickness of about 550 nm.

[0048] 8. The temperature of the reaction chamber is lowered to 1100°C, the pressure of the reaction chamber is increased to 600 mbar, the rotation speed of the large disk is set to 600 r / h, ammonia and trimethylgallium are introduced, and a GaN seed crystal bedding roughening layer 7 with a thickness of about 150 nm is grown on the basis of the low Al component AlGaN stress release layer 6.

[0049] 9. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 200 mbar, set the rotation speed of the large plate to 1200 r / h, continue to introduce ammonia and trimethylgallium, and grow a GaN epitaxial layer 8 on the basis of the GaN seed crystal roughening layer 7, with a thickness of about 1300 nm.

[0050] 10. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 100 mbar, introduce ammonia and trimethylaluminum, and grow a first AlN insertion layer 9 on the basis of the GaN epitaxial layer 8 with a thickness of about 10 nm.

[0051] 11. Keep the temperature of the reaction chamber constant, raise the pressure of the reaction chamber to 150 mbar, introduce ammonia, trimethylgallium, and ethylene, and set the growth rate in three stages, with a growth rate of 1 μm / h in the first stage, 2.5 μm / h in the second stage, and 4 μm / h in the third stage. First, C element is incorporated by δ doping to grow a C doped layer with a thickness of 2.5 nm, then C element doping is interrupted to grow a non-doped layer with a thickness of 35 nm, and the above steps are repeated to grow 15 groups of alternating C doped layers and non-doped layers, and a first C doped GaN layer 10 is grown on the basis of the first AlN insertion layer 9.

[0052] 12. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 100 mbar, introduce ammonia and trimethylaluminum, and grow a second AlN insertion layer 11 on the basis of the first C-doped GaN layer 10 with a thickness of about 10 nm.

[0053] 13. Keep the temperature of the reaction chamber constant, raise the pressure of the reaction chamber to 150 mbar, introduce ammonia, trimethylgallium, and ethylene, and set the growth rate in three stages, with a growth rate of 1 μm / h in the first stage, 2.5 μm / h in the second stage, and 4 μm / h in the third stage. First, C element is incorporated by δ doping to grow a C doped layer with a thickness of 2.5 nm, then C element doping is interrupted to grow a non-doped layer with a thickness of 35 nm, and the above steps are repeated to grow 15 groups of alternating C doped layers and non-doped layers, and a second C doped GaN layer 12 is grown on the basis of the second AlN insertion layer 11, with a thickness of about 1 μm.

[0054] 14. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 100 mbar, introduce ammonia and trimethylaluminum, and grow a third AlN insertion layer 13 on the second C-doped GaN layer 12 with a thickness of about 15 nm.

[0055] 15. Keep the temperature of the reaction chamber unchanged, increase the pressure of the reaction chamber to 200 mbar, stop introducing ethylene, continue to introduce ammonia and trimethylgallium, and grow an undoped GaN channel layer 14 on the third AlN insertion layer 13 with a thickness of about 350 nm.

[0056] 16. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 100 mbar, introduce ammonia and trimethylaluminum, and grow a fourth AlN insertion layer 15 on the undoped GaN channel layer 14 with a thickness of about 15 nm.

[0057] 17. The temperature of the reaction chamber is lowered to 1000° C., the pressure of the reaction chamber is maintained at 100 mbar, trimethylgallium and trimethylaluminum are introduced, and an AlGaN barrier layer 16 with an Al content of about 20% and a thickness of about 25 nm is grown on the fourth AlN insertion layer 15 .

[0058] 18. The temperature of the reaction chamber is raised to 1100° C., the pressure of the reaction chamber is increased to 200 mbar, ammonia and trimethylgallium are introduced, and a GaN capacitor layer 17 is grown on the AlGaN barrier layer 16 with a thickness of about 2.5 nm.

[0059] Example 3

[0060] A method for growing a silicon-based AlGaN / GaN HEMT epitaxial structure in this embodiment includes the following steps: 1. Place a (111) lightly doped silicon wafer on a graphite tray and then put it into the reaction chamber of the MOCVD system; raise the temperature of the MOCVD reaction chamber to 1300°C, set the reaction chamber pressure to 200 mbar, and set the plate speed to 1200r / h. Introduce hydrogen to perform high-temperature surface purification on the surface of the silicon substrate 1 for 500s to remove oxygen impurities, open the surface floating bonds, and make the surface full of activity.

[0061] 2. Stop the introduction of hydrogen, set the reaction chamber temperature to 1000° C., the reaction chamber pressure to 100 mbar, introduce trimethylaluminum into the reaction chamber for 30 seconds, and pre-spread Al source on the surface of the silicon substrate 1.

[0062] 3. The reaction chamber temperature is set to 700° C., the reaction chamber pressure is set to 100 mbar, ammonia is introduced for pre-nitridation, and then trimethylaluminum is introduced to grow a first AlN buffer layer 2 on the basis of the silicon substrate 1, with an epitaxial thickness of about 30 nm.

[0063] 4. The reaction chamber temperature is set to 1200° C., the reaction chamber pressure is set to 100 mbar, and trimethylaluminum is continuously introduced to grow a second AlN buffer layer 3 on the basis of the first AlN buffer layer 2, with an epitaxial thickness of about 200 nm.

[0064] 5. The temperature of the reaction chamber is raised to 1200° C., the pressure of the reaction chamber is set to 100 mbar, ammonia, trimethylgallium and trimethylaluminum are introduced, and a high Al component AlGaN stress release layer 4 with an Al molar content of about 50% and a thickness of about 100 nm is grown on the basis of the second AlN buffer layer 3.

[0065] 6. Maintaining the temperature and pressure of the reaction chamber unchanged, reducing the amount of trimethylaluminum introduced, and growing a medium Al component AlGaN stress release layer 5 with an Al molar content of about 40% on the basis of the high Al component AlGaN stress release layer 4, with a thickness of about 200 nm.

[0066] 7. Maintaining the temperature and pressure of the reaction chamber unchanged, continue to reduce the amount of trimethylaluminum introduced, and grow a low Al component AlGaN stress release layer 6 with an Al molar content of about 20% on the basis of the medium Al component AlGaN stress release layer 5, with a thickness of about 600 nm.

[0067] 8. The temperature of the reaction chamber is lowered to 1100°C, the pressure of the reaction chamber is increased to 600 mbar, the rotation speed of the large plate is set to 600 r / h, ammonia and trimethylgallium are introduced, and a GaN seed crystal bedding roughening layer 7 with a thickness of about 200 nm is grown on the basis of the low Al component AlGaN stress release layer 6.

[0068] 9. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 200 mbar, set the rotation speed of the large plate to 1200 r / h, continue to introduce ammonia and trimethylgallium, and grow a GaN epitaxial layer 8 on the basis of the GaN seed crystal roughening layer 7, with a thickness of about 1500 nm.

[0069] 10. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 100 mbar, introduce ammonia and trimethylaluminum, and grow a first AlN insertion layer 9 on the basis of the GaN epitaxial layer 8 with a thickness of about 10 nm.

[0070] 11. Keep the temperature of the reaction chamber constant, raise the pressure of the reaction chamber to 200 mbar, introduce ammonia, trimethylgallium, and ethylene, and set the growth rate in three stages, with the growth rate of the first stage being 1.2 μm / h, the growth rate of the second stage being 3 μm / h, and the growth rate of the third stage being 5 μm / h. First, C element is incorporated by δ doping to grow a C doped layer with a thickness of 3 nm, then C element doping is interrupted to grow a non-doped layer with a thickness of 50 nm, and the above steps are repeated to grow 20 sets of alternating stacked C doped layers and non-doped layers, and the first C doped GaN layer 10 is grown on the basis of the first AlN insertion layer 9.

[0071] 12. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 100 mbar, introduce ammonia and trimethylaluminum, and grow a second AlN insertion layer 11 on the basis of the first C-doped GaN layer 10 with a thickness of about 10 nm.

[0072] 13. Keep the temperature of the reaction chamber constant, increase the pressure of the reaction chamber to 200 mbar, introduce ammonia, trimethylgallium, and ethylene, and set the growth rate in three stages, with the growth rate of the first stage being 1.2 μm / h, the growth rate of the second stage being 3 μm / h, and the growth rate of the third stage being 5 μm / h. First, C element is incorporated by δ doping to grow a C doped layer with a thickness of 3 nm, then C element doping is interrupted to grow a non-doped layer with a thickness of 50 nm, and the above steps are repeated to grow 20 sets of alternating stacked C doped layers and non-doped layers, and a second C doped GaN layer 12 is grown on the basis of the second AlN insertion layer 11.

[0073] 14. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 100 mbar, introduce ammonia and trimethylaluminum, and grow a third AlN insertion layer 13 on the second C-doped GaN layer 12 with a thickness of about 20 nm.

[0074] 15. Keep the temperature of the reaction chamber unchanged, increase the pressure of the reaction chamber to 200 mbar, stop introducing ethylene, continue to introduce ammonia and trimethylgallium, and grow an undoped GaN channel layer 14 on the third AlN insertion layer 13 with a thickness of about 400 nm.

[0075] 16. Keep the temperature of the reaction chamber unchanged, reduce the pressure of the reaction chamber to 100 mbar, introduce ammonia and trimethylaluminum, and grow a fourth AlN insertion layer 15 on the undoped GaN channel layer 14 with a thickness of about 20 nm.

[0076] 17. The temperature of the reaction chamber is lowered to 1000° C., the pressure of the reaction chamber is maintained at 100 mbar, trimethylgallium and trimethylaluminum are introduced, and an AlGaN barrier layer 16 with an Al content of about 20% and a thickness of about 30 nm is grown on the fourth AlN insertion layer 15 .

[0077] 18. The temperature of the reaction chamber is raised to 1100° C., the pressure of the reaction chamber is increased to 300 mbar, ammonia and trimethylgallium are introduced, and a GaN capacitor layer 17 is grown on the AlGaN barrier layer 16 with a thickness of about 3 nm.

[0078] In order to verify the effect of the C element delta doping method, the epitaxial wafers prepared by the continuous C doping method without C doping were compared with the embodiment of the present invention. Except for the C doping method, the other steps of the three epitaxial wafers are the same as those of the embodiment of the present invention. In the table, comparison groups 1, 2, and 3 are epitaxial wafers produced in embodiments 1, 2, and 3 and their comparative examples.

[0079] Table 1. XRD test comparison of different C-doped GaN epitaxial wafers

[0080] The lattice crystal plane index of the two crystal directions (002) and (102) of each epitaxial wafer was tested. The smaller the index value, the better the quality of the epitaxial wafer. It should be noted that although the lattice crystal plane index value of the epitaxial wafer without C doping is the lowest, the epitaxial wafer without C doping cannot prevent the loss of electrons, and the HEMT obtained is an invalid device. Therefore, C doping is a necessary step. How to make the lattice crystal plane index of the epitaxial wafer closer to the index without doping after C doping is a difficult problem that needs to be overcome. By comparing the lattice crystal plane index of the epitaxial wafer obtained by continuous C doping and C element δ doping of the present invention, it can be seen that the epitaxial wafer obtained by C element δ doping has a smaller index, better quality, and is closer to the epitaxial wafer obtained without C doping, which can prove that the present invention has achieved better results than the prior art.

[0081] like Figure 2 As shown, the three curves correspond to the XRD rocking curves of the Si-based GaN-HEMT epitaxial wafers obtained in Examples 1, 2, and 3, respectively. It can be seen from the figure that the GaN and AlGaN peaks of the obtained XRD graph are sharp and clear. There is no obvious difference in the test results of the epitaxial structures obtained in the three examples.

[0082] like Figure 3As shown in the figure, it is the TEM (transmission electron microscope) test result of the Si-based GaN-HEMT epitaxial wafer obtained in the present invention. It can be seen from the figure that within a larger scale range, the surface morphology is uniform and flat, and surface slip lines are occasionally seen; it can be seen from the figure that within a smaller scale range, the morphology of the surface slip lines is also within the normal range.

[0083] For the Si-based GaN-HEMT epitaxial wafer obtained in Example 1 of the present invention, the electron mobility, surface density and sheet resistance of the AlGaN / GaN heterointerface two-dimensional electron gas 2DEG (two-dimensional electron gas) were measured by Hall measurement at room temperature, and were 2200 cm2 / V•s, 9×10-12 / cm2, and 400 Ω / □, respectively, with a high-quality heterostructure and a high-conductivity 2DEG channel.

[0084] In view of the problem that conventional high-concentration continuous C doping has a strong probability of occupying N vacancies, which easily leads to the formation of lattice defects in GaN epitaxy, further forms dislocations with the epitaxy, and then forms epitaxial defects of GaN epitaxy, forming leakage channels of power devices, the present invention adopts δ doping of C elements in GaN epitaxy to effectively alleviate the dislocation of lattice defects, obtain a GaN epitaxial high-resistance layer with higher crystal quality, and obtain epitaxial crystal quality better than conventional C-doped GaN layers.

Claims

1. A silicon-based AlGaN / GaN HEMT epitaxial structure, comprising a silicon substrate, an AlN buffer layer, a stepped AlGaN stress release layer, a GaN seed pad roughening layer (7), a GaN epitaxial layer (8), a first AlN insertion layer (9), a first C-doped GaN layer (10), a second AlN insertion layer (11), a second C-doped GaN layer (12), a third AlN insertion layer (13), an undoped GaN channel layer (14), a fourth AlN insertion layer (15), an AlGaN barrier layer (16), and a GaN capacitor layer (17) stacked in sequence from bottom to top; characterized in that: The first C-doped GaN layer (10) and the second C-doped GaN layer (12) comprise a plurality of alternately stacked C-doped layers and non-doped layers, and the C element of the C-doped layer is incorporated in a delta-doping manner.

2. The silicon-based AlGaN / GaN HEMT epitaxial structure according to claim 1, characterized in that: The thickness of the C-doped layer is 2-3 nm, and the thickness of the non-doped layer is 20-50 nm.

3. The silicon-based AlGaN / GaN HEMT epitaxial structure according to claim 2, characterized in that: The thickness of the first C-doped GaN layer (10) and the second C-doped GaN layer (12) is 0.5-1 μm.

4. A method for growing a silicon-based AlGaN / GaN HEMT epitaxial structure according to any one of claims 1 to 3, characterized in that: The following steps are involved: S1, placing a silicon substrate into a reaction chamber, introducing hydrogen gas, and performing high-temperature surface passivation on the silicon substrate; S2, stop the introduction of hydrogen, introduce trimethylaluminum into the reaction chamber, and pre-spread Al source on the surface of the silicon substrate; S3, introducing ammonia gas into the reaction chamber, and then introducing trimethylaluminum to grow an AlN buffer layer on the silicon substrate; S4, introducing ammonia, trimethylgallium, and trimethylaluminum into the reaction chamber, and growing a stepped AlGaN stress release layer on the AlN buffer layer by adjusting the amount of trimethylaluminum introduced; S5, introducing ammonia and trimethylgallium into the reaction chamber to grow a GaN seed crystal pad roughening layer (7) on the stepped AlGaN stress release layer; S6, continuing to introduce ammonia and trimethylgallium into the reaction chamber to grow a GaN epitaxial layer (8) on the GaN seed crystal roughening layer (7); S7, introducing ammonia gas and trimethylaluminum into the reaction chamber to grow a first AlN insertion layer (9) on the GaN epitaxial layer (8); S8, introducing ammonia, trimethylgallium and ethylene into the reaction chamber, and setting the growth rate to be step growth, growing a first C-doped GaN layer (10) on the basis of the first AlN insertion layer (9), wherein the C element is incorporated by δ-doping; S9, introducing ammonia gas and trimethylaluminum into the reaction chamber to grow a second AlN insertion layer (11) on the basis of the first C-doped GaN layer (10); S10, introducing ammonia, trimethylgallium and ethylene into the reaction chamber, setting the growth rate to be step growth, growing a second C-doped GaN layer (12) on the basis of the second AlN insertion layer (11), wherein the C element is incorporated by δ-doping; S11, introducing ammonia gas and trimethylaluminum into the reaction chamber to grow a third AlN insertion layer (13) on the second C-doped GaN layer (12); S12, introducing ammonia gas and trimethylgallium into the reaction chamber to grow an undoped GaN channel layer (14) on the third AlN insertion layer (13); S13, introducing ammonia gas and trimethylaluminum into the reaction chamber to grow a fourth AlN insertion layer (15) on the undoped GaN channel layer (14); S14, introducing trimethylgallium and trimethylaluminum into the reaction chamber to grow an AlGaN barrier layer (16) on the fourth AlN insertion layer (15); S15, introducing ammonia gas and trimethylgallium into the reaction chamber to grow a GaN capacitor layer (17) on the AlGaN barrier layer (16).

5. The growth method according to claim 4, characterized in that In step S3, the reaction chamber temperature is first set to 600°C-700°C and the reaction chamber pressure is set to 100 mbar to grow a first AlN buffer layer (2); the reaction chamber temperature is then set to 1000°C-1200°C and the reaction chamber pressure remains unchanged to grow a second AlN buffer layer (3), the growth temperature of the first AlN buffer layer (2) being lower than the growth temperature of the second AlN buffer layer (3).

6. The growth method according to claim 4, characterized in that In step S4, the reaction chamber temperature is 1200° C., the reaction chamber pressure is 100 mbar, and the amount of trimethylaluminum introduced is gradually reduced to generate a high Al component AlGaN epitaxial layer (4) with an Al component molar content of 50%-70%, a medium Al component AlGaN epitaxial layer (5) with an Al component molar content of 40%-60%, and a low Al component AlGaN epitaxial layer (6) with an Al component molar content of 20%-30%.

7. The growth method according to claim 4, characterized in that In steps S8 and S10, a C element is first introduced by a delta doping method to grow a C-doped layer, and then the C element doping is interrupted to grow a non-doped layer, and a plurality of alternately stacked C-doped layers and non-doped layers are repeatedly grown, finally obtaining a first C-doped GaN layer (10) and a second C-doped GaN layer (12).

8. The growth method according to claim 4, characterized in that In steps S8 and S10, the growth rate is divided into three stages, the growth rate in the first stage is 0.8-1.2 μm / h, the growth rate in the second stage is 2-3 μm / h, and the growth rate in the third stage is 3-5 μm / h.

9. The growth method according to claim 4, characterized in that: In steps S8 and S10, the temperature of the reaction chamber is 1100° C., and the pressure of the reaction chamber is 100-200 mbar.

10. The growth method according to claim 4, characterized in that: In steps S7, S9, S11 and S13, the temperature of the reaction chamber is 1100°C and the pressure of the reaction chamber is 100 mbar.

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