Silicon-based AlGaN / GaN HEMT epitaxial structure based on C-step doping and growth method of silicon-based AlGaN / GaN HEMT epitaxial structure

Abstract

The invention discloses a silicon-based AlGaN / GaN HEMT epitaxial structure based on C step doping and a growth method of the silicon-based AlGaN / GaN HEMT epitaxial structure. The 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 comprises a plurality of first C-doped unit layers which are sequentially stacked from bottom to top, and the C doping concentrations of the plurality of first C-doped unit layers are sequentially increased from bottom to top; the second C-doped GaN layer comprises a plurality of second C-doped unit layers which are sequentially stacked from bottom to top, the C doping concentration of the second C-doped unit layers is sequentially increased from bottom to top, and the C doping concentration of any second C-doped unit layer is higher than that of any first C-doped unit layer.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of semiconductor manufacturing, and in particular to a silicon-based AlGaN / GaN HEMT epitaxial structure based on C-step doping and a growth method thereof. BACKGROUND

[0002] Up to now, silicon (Si) materials account for a large proportion in the semiconductor market and play a major role in the development process of semiconductor technology, but due to the low theoretical limit of Si materials, the current low energy consumption cannot be met, and people gradually turn their attention to the third-generation wide-bandgap semiconductor materials with high thermal conductivity, high electron saturation speed and high breakdown field strength.

[0003] As a typical third-generation semiconductor power device, GaN-HEMT benefits from the unique wide bandgap, high electron saturation drift rate and high critical breakdown field of GaN materials, so that the AlGaN / GaN heterojunction has a high-concentration and high-mobility two-dimensional electron gas, thereby having the advantages of high power density, high breakdown voltage and low on-resistance, and is widely used in aerospace, 5G base stations and new energy vehicle fields.

[0004] Si-based GaN has a higher cost advantage than SiC substrates and GaN self-supporting substrates, but due to the large lattice mismatch and thermal mismatch coefficient between Si substrates and GaN, stress mismatch gradually occurs in epitaxy, forming a large number of dislocation groups in epitaxial growth, causing surface abnormalities such as epitaxial layer cracking, 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 to reduce the crystal defects of the Si-based GaN epitaxial material is the key to the application of Si-based GaN-HEMT in the radio frequency and power fields. SUMMARY

[0006] The application provides a silicon-based AlGaN / GaN HEMT epitaxial structure based on C-step doping.

[0007] The AlGaN / GaN HEMT epitaxial structure and the growth method thereof reduce the lattice mismatch caused by lattice vacancies due to doping to reduce the lattice defects of the epitaxial material.

[0008] Technical scheme: To solve the above problems, the application adopts a silicon-based AlGaN / GaN HEMT epitaxial structure based on C-step doping.

[0009] The AlGaN / GaN HEMT epitaxial structure comprises, from bottom to top, a silicon substrate, an AlN buffer layer, a stepped AlGaN stress release layer, a GaN seed 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; the first C-doped GaN layer comprises a plurality of first C-doped unit layers stacked from bottom to top, and the C-doping concentration of the plurality of first C-doped unit layers increases from bottom to top; the second C-doped GaN layer comprises a plurality of second C-doped unit layers stacked from bottom to top, and the C-doping concentration of the plurality of second C-doped unit layers increases from bottom to top, and the C-doping concentration of any second C-doped unit layer is higher than the C-doping concentration of any first C-doped unit layer.

[0010] Further, the first C-doped GaN layer comprises three first C-doped unit layers, and the C-doping concentration increases from bottom to top and is 6E17-8E17 atoms / cm 3 , 2E18-4E18 atoms / cm 3 , 6E18-8E18 atoms / cm 3 .

[0011] Further, the second C-doped GaN layer comprises two second C-doped unit layers, and the C-doping concentration increases from bottom to top and is 8E18-1E19 atoms / cm 3 , 2E19-3E19 atoms / cm 3 .

[0012] Further, the thickness of the first C-doped GaN layer and the second C-doped GaN layer is 0.5-1 μm.

[0013] The application further provides a growth method of the silicon-based AlGaN / GaN HEMT epitaxial structure, comprising the following steps:

[0014] S1, placing a silicon substrate into a reaction cavity, introducing hydrogen, and performing high-temperature surface passivation on the silicon substrate;

[0015] S2, stopping the introduction of hydrogen, introducing trimethylaluminum into the reaction cavity, and pre-depositing an Al source on the surface of the silicon substrate;

[0016] S3, introducing ammonia and then trimethylaluminum into the reaction cavity, and growing an AlN buffer layer on the silicon substrate;

[0017] S4, introducing ammonia, trimethylgallium and trimethylaluminum into the reaction cavity, and growing a stepped AlGaN stress release layer on the AlN buffer layer by adjusting the amount of trimethylaluminum introduced.

[0018] S5, introducing ammonia and trimethyl gallium into the reaction cavity to grow a GaN seed layer on the step AlGaN stress release layer;

[0019] S6, continuously introducing ammonia and trimethyl gallium into the reaction cavity to grow a GaN epitaxial layer on the GaN seed layer;

[0020] S7, introducing ammonia and trimethyl aluminum into the reaction cavity to grow a first AlN insertion layer on the GaN epitaxial layer;

[0021] S8, introducing ammonia, trimethyl gallium and ethylene into the reaction cavity to grow a plurality of first C-doped unit layers with C-doped concentrations increasing from bottom to top on the basis of the first AlN insertion layer by controlling the concentration of ethylene introduced;

[0022] S9, introducing ammonia and trimethyl aluminum into the reaction cavity to grow a second AlN insertion layer on the basis of the first C-doped GaN layer;

[0023] S10, introducing ammonia, trimethyl gallium and ethylene into the reaction cavity to grow a plurality of second C-doped unit layers with C-doped concentrations increasing from bottom to top on the basis of the second AlN insertion layer by controlling the concentration of ethylene introduced;

[0024] S11, introducing ammonia and trimethyl aluminum into the reaction cavity to grow a third AlN insertion layer on the second C-doped GaN layer;

[0025] S12, introducing ammonia and trimethyl gallium into the reaction cavity to grow an undoped GaN channel layer on the third AlN insertion layer;

[0026] S13, introducing ammonia and trimethyl aluminum into the reaction cavity to grow a fourth AlN insertion layer on the undoped GaN channel layer;

[0027] S14, introducing trimethyl gallium and trimethyl aluminum into the reaction cavity to grow an AlGaN barrier layer on the fourth AlN insertion layer;

[0028] S15, introducing ammonia and trimethyl gallium into the reaction cavity to grow a GaN capacitor layer on the AlGaN barrier layer.

[0029] Further, in step S3, the reaction cavity temperature is first set to 600-700℃ and the reaction cavity pressure is 100mbar to grow the first AlN buffer layer; then the reaction cavity temperature is set to 1000-1200℃ and the reaction cavity pressure remains unchanged to grow the second AlN buffer layer, and the growth temperature of the first AlN buffer layer is lower than that of the second AlN buffer layer.

[0030] Further, in step S4, the reaction cavity temperature is 1200℃, the reaction cavity pressure is 100mbar, and the amount of trimethylaluminum gradually decreases to generate an Al component AlGaN epitaxial layer with a molar content of 50%-70% of Al component, an Al component AlGaN epitaxial layer with a molar content of 40%-60% of Al component, and an Al component AlGaN epitaxial layer with a molar content of 20%-30% of Al component.

[0031] Further, in steps S8 and S10, the ethylene concentration gradually increases to grow the first C-doped unit layer and the second C-doped unit layer.

[0032] Further, in steps S8 and S10, the reaction cavity temperature is 1100℃, and the reaction cavity pressure is 100-200mbar.

[0033] Further, in steps S7, S9, S11 and S13, the reaction cavity temperature is 1100℃, and the reaction cavity pressure is 100mbar.

[0034] Beneficial effects: Compared with the prior art, the present application has the following advantages: the C element concentration step doping in GaN epitaxy effectively alleviates the absence of lattice defects, reduces the dislocation density in GaN epitaxy, lays a foundation for the growth of GaN layers and AlGaN two-dimensional electron gas layers in nitride thin film structure layers, and ultimately improves the quality of Si-based GaN epitaxial materials, achieves high crystal quality, high pressure resistance and no leakage of epitaxial wafers, obtains GaN epitaxial high resistance layers with high crystal quality, and obtains better epitaxial crystal quality than conventional C-doped GaN layers. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The overall structure of the epitaxial wafer prepared by the present application is shown in the figure.

[0036] Figure 2 The XRD rocking curve comparison diagram of the epitaxial wafer prepared by the embodiment of the present application and the conventional process is shown in the figure. DETAILED DESCRIPTION

[0037] The equipment used for epitaxial structure growth of the present application 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 ethylene (C2H4), the nitrogen source (group V source) is ammonia (NH3), the gallium source is trimethylgallium (TMGa), and the aluminum source is trimethylaluminum (TMAl).

[0038] Example 1

[0039] The growth method of the silicon-based AlGaN / GaN HEMT epitaxial structure based on C-step doping in the embodiment comprises the following steps:

[0040] 1. Place a lightly doped silicon wafer with a (111) crystal orientation on a graphite tray, and then place it in the reaction chamber of a MOCVD system; increase the temperature of the MOCVD reaction chamber to 1100°C, set the reaction chamber pressure to 100 mbar, and set the large disc rotation speed to 1000 r / h. Introduce hydrogen gas to perform high-temperature surface purification on the surface of the silicon substrate 1 for a duration of 300 s to remove oxygen impurities and open the surface dangling bonds to make the surface full of activity.

[0041] 2. Stop the hydrogen gas introduction, set the reaction chamber temperature to 900°C, and set the reaction chamber pressure to 50 mbar. Introduce trimethylaluminum into the reaction chamber for a gas introduction time of 10 s to pre-deposit Al source on the surface of the silicon substrate 1.

[0042] 3. Set the reaction chamber temperature to 600°C and the reaction chamber pressure to 100 mbar. Introduce ammonia gas for pre-nitridation, and then introduce trimethylaluminum to grow a first AlN buffer layer 2 on the silicon substrate 1 with an epitaxial thickness of about 10 nm.

[0043] 4. Set the reaction chamber temperature to 1000°C and the reaction chamber pressure to 100 mbar. Continue to introduce trimethylaluminum to grow a second AlN buffer layer 3 on the first AlN buffer layer 2 with an epitaxial thickness of about 100 nm.

[0044] 5. Increase the reaction chamber temperature to 1200°C and set the reaction chamber pressure to 100 mbar. Introduce ammonia gas, trimethylgallium, and trimethylaluminum to grow a high-Al component AlGaN stress release layer 4 with an Al mole content of about 70% on the second AlN buffer layer 3 with a thickness of about 50 nm.

[0045] 6. Maintain the reaction chamber temperature and pressure unchanged, and reduce the trimethylaluminum introduction amount. Grow a medium-Al component AlGaN stress release layer 5 with an Al mole content of about 60% on the high-Al component AlGaN stress release layer 4 with a thickness of about 100 nm.

[0046] 7. Maintain the reaction chamber temperature and pressure unchanged, and continue to reduce the trimethylaluminum introduction amount. Grow a low-Al component AlGaN stress release layer 6 with an Al mole content of about 30% on the medium-Al component AlGaN stress release layer 5 with a thickness of about 500 nm.

[0047] 8. The temperature of the reaction cavity is reduced to 1100 °C, the pressure of the reaction cavity is increased to 600 mbar, the rotation speed of the large plate is set to 600 r / h, ammonia, trimethyl gallium are introduced, and a GaN seed matting coarsening layer 7 is grown on the basis of the low Al component AlGaN stress release layer 6, with a thickness of about 100 nm.

[0048] 9. The temperature of the reaction cavity is kept unchanged, the pressure of the reaction cavity is reduced to 200 mbar, the rotation speed of the large plate is set to 1200 r / h, ammonia, trimethyl gallium are continuously introduced, and a GaN epitaxial layer 8 is grown on the basis of the GaN seed matting coarsening layer 7, with a thickness of about 1000 nm.

[0049] 10. The temperature of the reaction cavity is kept unchanged, the pressure of the reaction cavity is reduced to 100 mbar, ammonia and trimethyl aluminum are introduced, and a first AlN insertion layer 9 is grown on the basis of the GaN epitaxial layer 8, with a thickness of about 10 nm.

[0050] 11. The temperature and pressure of the reaction cavity are kept unchanged, ammonia, trimethyl gallium, and ethylene are introduced, the concentration of the introduced ethylene is gradually increased, three first C-doped unit layers are generated and stacked in order from bottom to top, the C-doping concentration is 6E17 atoms / cm 3 , 2E18 atoms / cm 3 , 6E18 atoms / cm 3 from bottom to top, and the thicknesses of the three first C-doped unit layers are substantially equal. A first C-doped GaN layer 10 with a thickness of 0.5 μm is grown on the basis of the first AlN insertion layer 9.

[0051] 12. The temperature and pressure of the reaction cavity are kept unchanged, ammonia and trimethyl aluminum are introduced, and a second AlN insertion layer 11 is grown on the basis of the first C-doped GaN layer 10, with a thickness of about 10 nm.

[0052] 13. The temperature and pressure of the reaction cavity are kept unchanged, ammonia, trimethyl gallium, and ethylene are introduced, the concentration of the introduced ethylene is gradually increased, two second C-doped unit layers are generated and stacked in order from bottom to top, the C-doping concentration is 8E18 atoms / cm 3 , 2E19 atoms / cm 3 from bottom to top, and the thicknesses of the two second C-doped unit layers are equal. A second C-doped GaN layer 12 with a thickness of 0.5 μm is grown on the basis of the second AlN insertion layer 11.

[0053] 14. The temperature and pressure of the reaction cavity are kept unchanged, ammonia and trimethyl aluminum are introduced, and a third AlN insertion layer 13 is grown on the basis of the second C-doped GaN layer 12, with a thickness of about 10 nm.

[0054] 15. The temperature of the reaction cavity is kept unchanged, the pressure of the reaction cavity is increased to 200 mbar, the ethylene is stopped, the ammonia and trimethyl gallium are continuously introduced, and the undoped GaN channel layer 14 with a thickness of about 300 nm is grown on the third AlN interlayer 13.

[0055] 16. The temperature of the reaction cavity is kept unchanged, the pressure of the reaction cavity is decreased to 100 mbar, the ammonia and trimethyl aluminum are introduced, and the fourth AlN interlayer 15 with a thickness of about 10 nm is grown on the undoped GaN channel layer 14.

[0056] 17. The temperature of the reaction cavity is decreased to 1000℃, the pressure of the reaction cavity is kept at 100 mbar, the trimethyl gallium and trimethyl aluminum are introduced, and the AlGaN barrier layer 16 with an Al content of about 20% and a thickness of about 20 nm is grown on the fourth AlN interlayer 15.

[0057] 18. The temperature of the reaction cavity is increased to 1100℃, the pressure of the reaction cavity is increased to 150 mbar, the ammonia and trimethyl gallium are introduced, and the GaN capacitor layer 17 with a thickness of about 2 nm is grown on the AlGaN barrier layer 16.

[0058] Finally, the epitaxial structure shown in Figure 1 is obtained.

[0059] Example 2

[0060] A growth method of a silicon-based AlGaN / GaN HEMT epitaxial structure based on C-step doping in the embodiment includes the following steps:

[0061] 1. A lightly doped silicon wafer with a (111) crystal orientation is placed on a graphite tray and then placed in the reaction cavity of a MOCVD system; the temperature of the MOCVD reaction cavity is increased to 1200℃, the pressure of the reaction cavity is set to 150 mbar, and the large disc rotation speed is set to 1100 r / h. Hydrogen is introduced to perform high-temperature surface purification on the surface of the silicon substrate 1 for a duration of 400 s to remove oxygen impurities and open the surface dangling bonds to make the surface full of activity.

[0062] 2. The hydrogen introduction is stopped, the temperature of the reaction cavity is set to 950℃, the pressure of the reaction cavity is set to 75 mbar, trimethyl aluminum is introduced into the reaction cavity, and the gas introduction time is 20 s to pre-deposit Al source on the surface of the silicon substrate 1.

[0063] 3. The temperature of the reaction cavity is set to 650℃, the pressure of the reaction cavity is set to 100 mbar, ammonia is introduced for pre-nitridation, and then trimethyl aluminum is introduced to grow the first AlN buffer layer 2 on the basis of the silicon substrate 1 with an epitaxial thickness of about 20 nm.

[0064] 4、Set the temperature of the reaction cavity to 1100℃, set the pressure of the reaction cavity to 100mbar, continue to input trimethylaluminum, grow a second AlN buffer layer 3 on the basis of the first AlN buffer layer 2, and the epitaxial thickness is about 150nm.

[0065] 5、Increase the temperature of the reaction cavity to 1200℃, set the pressure of the reaction cavity to 100mbar, input ammonia, trimethylgallium and trimethylaluminum, grow a high Al component AlGaN stress release layer 4 with an Al mole content of about 60% on the basis of the second AlN buffer layer 3, and the thickness is about 75nm.

[0066] 6、Maintain the temperature and pressure of the reaction cavity unchanged, reduce the input amount of trimethylaluminum, grow a medium Al component AlGaN stress release layer 5 with an Al mole content of about 50% on the basis of the high Al component AlGaN stress release layer 4, and the thickness is about 150nm.

[0067] 7、Maintain the temperature and pressure of the reaction cavity unchanged, continue to reduce the input amount of trimethylaluminum, grow a low Al component AlGaN stress release layer 6 with an Al mole content of about 25% on the basis of the medium Al component AlGaN stress release layer 5, and the thickness is about 550nm.

[0068] 8、Reduce the temperature of the reaction cavity to 1100℃, increase the pressure of the reaction cavity to 600mbar, set the rotation speed of the large disc to 600r / h, input ammonia and trimethylgallium, grow a GaN seed mat roughening layer 7 on the basis of the low Al component AlGaN stress release layer 6, and the thickness is about 150nm.

[0069] 9、Maintain the temperature of the reaction cavity unchanged, reduce the pressure of the reaction cavity to 200mbar, set the rotation speed of the large disc to 1200r / h, continue to input ammonia and trimethylgallium, grow a GaN epitaxial layer 8 on the basis of the GaN seed mat roughening layer 7, and the thickness is about 1300nm.

[0070] 10、Maintain the temperature of the reaction cavity unchanged, reduce the pressure of the reaction cavity to 100mbar, input ammonia and trimethylaluminum, grow a first AlN insertion layer 9 on the basis of the GaN epitaxial layer 8, and the thickness is about 10nm.

[0071] 11、Maintain the temperature of the reaction cavity unchanged, increase the pressure of the reaction cavity to 150mbar, input ammonia, trimethylgallium and ethylene, control the gradually increasing concentration of ethylene input, generate three first C-doped unit layers stacked from bottom to top, and the C-doping concentration from bottom to top is 7E17 atoms / cm 3 , 3E18 atoms / cm 3 , 7E18 atoms / cm 3The three first C-doped unit layers have equal thicknesses, and a first C-doped GaN layer 10 with a thickness of 0.75 μm is grown on the basis of the first AlN insertion layer 9.

[0072] 12. Keep the reaction chamber temperature constant, reduce the reaction chamber pressure to 100 mbar, introduce ammonia and trimethylaluminum, and grow a second AlN insertion layer 11 with a thickness of about 10 nm on the basis of the first C-doped GaN layer 10.

[0073] 13. Keeping the reaction chamber temperature constant, increase the reaction chamber pressure to 150 mbar, and introduce ammonia, trimethylgallium, and ethylene to generate two second C-doped unit layers stacked sequentially from bottom to top. The C doping concentration from bottom to top is 9E18 atoms / cm³. 3 2.5E19 atoms / cm 3 The two second C-doped unit layers have equal thicknesses, and a second C-doped GaN layer 12 with a thickness of 0.75 μm is grown on the basis of the second AlN insertion layer 11.

[0074] 14. Keep the reaction chamber temperature constant, reduce the reaction chamber pressure to 100 mbar, introduce ammonia and trimethylaluminum, and grow a third AlN insertion layer 13 with a thickness of about 15 nm on the second C-doped GaN layer 12.

[0075] 15. Keep the reaction chamber temperature constant, increase the reaction chamber pressure to 200 mbar, stop the ethylene supply, and continue to supply ammonia and trimethylgallium to grow an undoped GaN channel layer 14 with a thickness of approximately 350 nm on the third AlN insertion layer 13.

[0076] 16. Keeping the reaction chamber temperature constant, reduce the reaction chamber pressure to 100 mbar, introduce ammonia and trimethylaluminum, and grow a fourth AlN insertion layer 15 with a thickness of about 15 nm on the undoped GaN channel layer 14.

[0077] 17. Reduce the temperature of the reaction chamber to 1000℃, maintain the pressure of the reaction chamber at 100mbar, and introduce trimethylgallium and trimethylaluminum to grow an AlGaN barrier layer 16 with an Al content of about 20% and a thickness of about 25nm on the fourth AlN insertion layer 15.

[0078] 18. Raise the temperature of the reaction chamber to 1100℃ and the pressure of the reaction chamber to 200mbar. Introduce ammonia and trimethylgallium to grow a GaN capacitor layer 17 with a thickness of about 2.5nm on the AlGaN barrier layer 16.

[0079] Example 3

[0080] The growth method of the silicon-based AlGaN / GaN HEMT epitaxial structure based on C-step doping in the embodiment comprises the following steps:

[0081] 1. Place a lightly doped silicon wafer with a (111) crystal orientation on a graphite tray, and then place it in the reaction chamber of a MOCVD system; increase the temperature of the MOCVD reaction chamber to 1300°C, set the reaction chamber pressure to 200 mbar, and set the large plate rotation speed to 1200 r / h. Introduce hydrogen to perform high-temperature surface purification on the surface of the silicon substrate 1 for a duration of 500 s to remove oxygen impurities and open the surface dangling bonds to make the surface full of activity.

[0082] 2. Stop the hydrogen introduction, set the reaction chamber temperature to 1000°C, and set the reaction chamber pressure to 100 mbar. Introduce trimethylaluminum into the reaction chamber for a gas introduction time of 30 s to pre-deposit Al source on the surface of the silicon substrate 1.

[0083] 3. Set the reaction chamber temperature to 700°C and the reaction chamber pressure to 100 mbar. Introduce ammonia for pre-nitridation, and then introduce trimethylaluminum to grow a first AlN buffer layer 2 on the silicon substrate 1 with an epitaxial thickness of about 30 nm.

[0084] 4. Set the reaction chamber temperature to 1200°C and the reaction chamber pressure to 100 mbar. Continue to introduce trimethylaluminum to grow a second AlN buffer layer 3 on the first AlN buffer layer 2 with an epitaxial thickness of about 200 nm.

[0085] 5. Increase the reaction chamber temperature to 1200°C and set the reaction chamber pressure to 100 mbar. Introduce ammonia, trimethylgallium, and trimethylaluminum to grow a high-Al component AlGaN stress release layer 4 with an Al molar content of about 50% and a thickness of about 100 nm on the second AlN buffer layer 3.

[0086] 6. Maintain the reaction chamber temperature and pressure unchanged, and reduce the trimethylaluminum introduction amount. Grow a medium-Al component AlGaN stress release layer 5 with an Al molar content of about 40% and a thickness of about 200 nm on the high-Al component AlGaN stress release layer 4.

[0087] 7. Maintain the reaction chamber temperature and pressure unchanged, and continue to reduce the trimethylaluminum introduction amount. Grow a low-Al component AlGaN stress release layer 6 with an Al molar content of about 20% and a thickness of about 600 nm on the medium-Al component AlGaN stress release layer 5.

[0088] 8. The temperature of the reaction cavity is reduced to 1100 °C, the pressure of the reaction cavity is increased to 600 mbar, the rotation speed of the large plate is set to 600 r / h, ammonia, trimethyl gallium are introduced, and a GaN seed matting coarsening layer 7 with a thickness of about 200 nm is grown on the basis of the low Al component AlGaN stress release layer 6.

[0089] 9. The temperature of the reaction cavity is kept unchanged, the pressure of the reaction cavity is reduced to 200 mbar, the rotation speed of the large plate is set to 1200 r / h, ammonia, trimethyl gallium are continuously introduced, and a GaN epitaxial layer 8 with a thickness of about 1500 nm is grown on the basis of the GaN seed matting coarsening layer 7.

[0090] 10. The temperature of the reaction cavity is kept unchanged, the pressure of the reaction cavity is reduced to 100 mbar, ammonia and trimethyl aluminum are introduced, and a first AlN insertion layer 9 with a thickness of about 10 nm is grown on the basis of the GaN epitaxial layer 8.

[0091] 11. The temperature of the reaction cavity is kept unchanged, the pressure of the reaction cavity is increased to 200 mbar, ammonia, trimethyl gallium, ethylene are introduced, the concentration of the introduced ethylene is gradually increased, three first C-doped unit layers are generated, the C-doped concentration from bottom to top is 8E17 atoms / cm 3 , 4E18 atoms / cm 3 , 8E18 atoms / cm 3 , the thicknesses of the three first C-doped unit layers are substantially equal, and a first C-doped GaN layer 10 with a thickness of 1 μm is grown on the basis of the first AlN insertion layer 9.

[0092] 12. The temperature of the reaction cavity is kept unchanged, the pressure of the reaction cavity is reduced to 100 mbar, ammonia, trimethyl aluminum are introduced, and a second AlN insertion layer 11 with a thickness of about 10 nm is grown on the basis of the first C-doped GaN layer 10.

[0093] 13. The temperature of the reaction cavity is kept unchanged, the pressure of the reaction cavity is increased to 200 mbar, ammonia, trimethyl gallium, ethylene are introduced, the concentration of the introduced ethylene is gradually increased, two second C-doped unit layers are generated, the C-doped concentration from bottom to top is 1E19 atoms / cm 3 , 3E19 atoms / cm 3 , the thicknesses of the two second C-doped unit layers are equal, and a second C-doped GaN layer 12 with a thickness of 1 μm is grown on the basis of the second AlN insertion layer 11.

[0094] 14. The temperature of the reaction cavity is kept unchanged, the pressure of the reaction cavity is reduced to 100 mbar, ammonia, trimethyl aluminum are introduced, and a third AlN insertion layer 13 with a thickness of about 20 nm is grown on the second C-doped GaN layer 12.

[0095] 15. Keep the reaction chamber temperature constant, increase the reaction chamber pressure to 200 mbar, stop the ethylene supply, and continue to supply ammonia and trimethylgallium to grow an undoped GaN channel layer 14 with a thickness of about 400 nm on the third AlN insertion layer 13.

[0096] 16. Keeping the reaction chamber temperature constant, reduce the reaction chamber pressure to 100 mbar, introduce ammonia and trimethylaluminum, and grow a fourth AlN insertion layer 15 with a thickness of about 20 nm on the undoped GaN channel layer 14.

[0097] 17. Reduce the temperature of the reaction chamber to 1000℃, maintain the pressure of the reaction chamber at 100mbar, and introduce trimethylgallium and trimethylaluminum to grow an AlGaN barrier layer 16 with an Al content of about 20% and a thickness of about 30nm on the fourth AlN insertion layer 15.

[0098] 18. Raise the temperature of the reaction chamber to 1100℃ and the pressure of the reaction chamber to 300mbar. Introduce ammonia and trimethylgallium to grow a GaN capacitor layer 17 with a thickness of about 3nm on the AlGaN barrier layer 16.

[0099] like Figure 2 The figure shows the XRD rocking curves of silicon-based GaN-HEMT epitaxial wafers obtained in the embodiments of the present invention. The red curve represents the sample prepared using the conventional C-element continuous high-doping GaN process, and the three dark curves represent the samples prepared in Examples 1-3. The first peak in the figure is the GaN peak, and its half-width at half-maximum (WHM) is an important parameter reflecting sample quality. It can be seen from the figure that the WHM of the GaN peak in the samples prepared in Examples 1-3 of the present invention is smaller than that prepared using the conventional C-element continuous high-doping GaN process, indicating that the GaN crystal quality is improved after using the C-step doping process of the present invention. Among them, the curve in Example 2 has the narrowest WHM, while the WHMs of Examples 1 and 3 are basically equal.

[0100] The electron mobility, areal density, and sheet resistance of the silicon-based GaN-HEMT epitaxial wafer obtained in this invention, measured by Hall effect at room temperature, are shown in the table below:

[0101] electron mobility (cm 2 / V·s)]]> Area density ( / cm 2 ) Sheet resistance (Ω / cm 2) ]] Example 1 1700 9.2 x 10 12 ]]> 400 Example 2 2150 9.7 x 10 12 ]]> 300 Example 3 1800 9.9 x 10 12 ]] 350

[0102] The epitaxial wafers prepared in the three embodiments all have high-quality heterostructures and highly conductive 2DEG channels. Among them, Embodiment 2 has the highest electron mobility and the lowest sheet resistance, achieving optimal performance.

Claims

1. A silicon-based AlGaN / GaN HEMT epitaxial structure based on C-step doping, comprising, from bottom to top, a silicon substrate, an AlN buffer layer, a step AlGaN stress release layer, a GaN seed paving coarsening layer (7), a GaN epitaxial layer (8), a first AlN interlayer (9), a first C-doped GaN layer (10), a second AlN interlayer (11), a second C-doped GaN layer (12), a third AlN interlayer (13), an undoped GaN channel layer (14), a fourth AlN interlayer (15), an AlGaN barrier layer (16), and a GaN capacitor layer (17); characterized in that, The first C-doped GaN layer (10) comprises a plurality of first C-doped unit layers stacked from bottom to top, and the C-doping concentration of the plurality of first C-doped unit layers increases from bottom to top; the second C-doped GaN layer (12) comprises a plurality of second C-doped unit layers stacked from bottom to top, and the C-doping concentration of the plurality of second C-doped unit layers increases from bottom to top, and the C-doping concentration of any second C-doped unit layer is higher than the C-doping concentration of any first C-doped unit layer.

2. The silicon-based AlGaN / GaN HEMT epitaxial structure of claim 1, wherein, The first C-doped GaN layer (10) includes three first C-doped unit layers, from bottom to top, the C-doping concentration is 6E17-8E17 atoms / cm 3 , 2E18-4E18 atoms / cm 3 , 6E18-8E18 atoms / cm 3 .

3. The silicon-based AlGaN / GaN HEMT epitaxial structure of claim 2, wherein, The second C-doped GaN layer (12) comprises two second C-doped unit layers, from bottom to top, the C-doping concentration is 8E18-1E19 atoms / cm 3 , 2E19-3E19 atoms / cm 3 .

4. The silicon-based AlGaN / GaN HEMT epitaxial structure of claim 1, wherein, The thickness of the first C-doped GaN layer (10) and the second C-doped GaN layer (12) is 0.5-1 μm.

5. A method for growing a silicon-based AlGaN / GaN HEMT epitaxial structure according to any one of claims 1 to 4, characterized in that, The method comprises the following steps: S1, placing a silicon substrate into a reaction cavity, introducing hydrogen, and performing high-temperature surface passivation on the silicon substrate; S2, stopping the introduction of hydrogen, introducing trimethylaluminum into the reaction cavity, and pre-depositing an Al source on the surface of the silicon substrate; S3, introducing ammonia and then trimethylaluminum into the reaction cavity, and growing an AlN buffer layer on the silicon substrate; S4, introducing ammonia, trimethylgallium, and trimethylaluminum into the reaction cavity, 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 cavity, and growing a GaN seed mat roughening layer (7) on the stepped AlGaN stress release layer; S6, continuously introducing ammonia and trimethylgallium into the reaction cavity, and growing a GaN epitaxial layer (8) on the GaN seed mat roughening layer (7); S7, introducing ammonia and trimethylaluminum into the reaction cavity, and growing a first AlN insertion layer (9) on the GaN epitaxial layer (8); S8, introducing ammonia, trimethylgallium, and ethylene into the reaction cavity, and growing a plurality of first C-doped unit layers with C-doping concentration increasing from bottom to top on the basis of the first AlN insertion layer (9) by controlling the concentration of ethylene introduced; S9, introducing ammonia and trimethylaluminum into the reaction cavity, and growing 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 cavity, and growing a plurality of second C-doped unit layers with C-doping concentration increasing from bottom to top on the basis of the second AlN insertion layer (11) by controlling the concentration of ethylene introduced; S11, introducing ammonia and trimethylaluminum into the reaction cavity, and growing a third AlN insertion layer (13) on the second C-doped GaN layer (12); S12, introducing ammonia and trimethylgallium into the reaction cavity, and growing an undoped GaN channel layer (14) on the third AlN insertion layer (13); S13, introducing ammonia and trimethylaluminum into the reaction cavity, and growing a fourth AlN insertion layer (15) on the undoped GaN channel layer (14); S14, introducing trimethylgallium and trimethylaluminum into the reaction cavity, and growing an AlGaN barrier layer (16) on the fourth AlN insertion layer (15); S15, introducing ammonia and trimethylgallium into the reaction cavity, and growing a GaN capacitor layer (17) on the AlGaN barrier layer (16).

6. The growth method of claim 5, wherein, In step S3, the temperature of the reaction cavity is set to 600-700 DEG C and the pressure of the reaction cavity is set to 100 mbar to grow the first AlN buffer layer (2); then the temperature of the reaction cavity is set to 1000-1200 DEG C and the pressure of the reaction cavity is kept unchanged to grow the second AlN buffer layer (3), and the growth temperature of the first AlN buffer layer (2) is lower than that of the second AlN buffer layer (3).

7. The growth method of claim 5, wherein, In step S4, the temperature of the reaction cavity is 1200 DEG C, the pressure of the reaction cavity is 100 mbar, and the amount of trimethylaluminum gradually decreases to generate the high Al component AlGaN epitaxial layer (4) with the Al component mole content of 50-70%, the middle Al component AlGaN epitaxial layer (5) with the Al component mole content of 40-60%, and the low Al component AlGaN epitaxial layer (6) with the Al component mole content of 20-30%.

8. The growth method of claim 5, wherein, In steps S8 and S10, the concentration of ethylene gradually increases to grow the first C-doped unit layer and the second C-doped unit layer.

9. The growth method of claim 5, wherein, In steps S8 and S10, the temperature of the reaction cavity is 1100 DEG C and the pressure of the reaction cavity is 100-200 mbar.

10. The growth method of claim 5, wherein, In steps S7, S9, S11 and S13, the temperature of the reaction cavity is 1100 DEG C and the pressure of the reaction cavity is 100 mbar.

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