A heavily doped p-type SiC single crystal and its growth method and application

Abstract

The present invention belongs to the field of semiconductor technology, and specifically relates to a heavily doped p-type SiC single crystal, and a growth method and application thereof. The present invention utilizes a compound or solid solution composed of aluminum and nitrogen elements as a type of doping source and other p-type doping sources as a type of doping source to perform Al-N co-doping. Furthermore, AlN material is placed in the SiC powder area as a type of doping source, so that when it decomposes, it provides Al atoms and N atoms in the same molar ratio, thereby achieving the synchronous release of the N source and the Al source, thereby maintaining the single crystal form of the heavily doped crystal; Al4C3, Al2O3, Al, etc. are placed as the second type of doping source to provide additional Al elements to achieve n[Al]:n[N] in the range of 1.2 to 3.0, ensuring that the grown crystal is a single crystal p-type SiC. The obtained p-type SiC single crystal has an Al doping concentration of not less than 7×10 19 cm ‑3 , resistivity not higher than 0.200Ω·cm, and half-peak width of the rocking curve not exceeding 60 arc seconds, can be applied to the fields of smart grid, photovoltaic power generation, high-power power electronic devices, etc.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductors, and in particular relates to a heavily doped p-type SiC single crystal and a growth method and application thereof. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance the understanding of the overall background of the invention, and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] As a typical representative of the third generation of semiconductor materials, silicon carbide (SiC) has excellent physical properties such as large bandgap, high carrier mobility, high critical breakdown electric field strength, and high thermal conductivity. It is very suitable for the preparation of high-temperature, high-frequency, and high-power semiconductor devices. Silicon carbide devices have important applications in aviation, aerospace exploration, new energy vehicles, 5G communications, power grid transmission, photovoltaic power generation, and other fields. SiC-based insulated-gate bipolar transistors (IGBTs) are composite fully controlled voltage-driven power semiconductor devices composed of bipolar transistors (BJTs) and insulated-gate field-effect transistors (MOS). They have the characteristics of high input impedance and low conduction voltage drop, and low conduction loss under high voltage environments. They are the focus of the development of substrate materials for the preparation of high-power power electronic devices in the future. Among them, p-type SiC substrates are the basic materials for the preparation of n-channel IGBTs. However, limited by the current doping technology, p-type SiC crystals still have problems such as poor crystal stability and high resistivity.

[0004] The main p-type doping elements for growing p-type SiC using a PVT growth device are Al, B, etc. Since the ionization energy of Al atoms in 4H-SiC is about 190meV and the ionization energy in 6H-SiC is about 240-290meV, Al is currently the element with the shallowest acceptor energy level introduced into the SiC bandgap, making it the preferred doping element for preparing p-type SiC. However, compared with the ionization energy of donor N atoms in SiC of 84-125meV, the ionization rate of Al atoms in SiC is relatively low. By heavily doping Al atoms (>7×10 19 cm -3 ) can realize acceptor energy level hybridization in the SiC bandgap, reduce the energy level position of the acceptor, and achieve the purpose of reducing the ionization energy of Al atoms. Therefore, the preparation of low resistivity p-type SiC is generally achieved by heavy doping. However, Al atoms occupy Si lattice points in the SiC unit cell, and the covalent bond radii of Al and Si atoms are 126pm and 117ppm respectively. Heavy doping of Al elements in SiC single crystals will cause the SiC unit cell to expand. Since the stacking fault energy between different SiC crystal forms is low, heavily doped p-type SiC single crystals are prone to heterogeneous polymorphism, resulting in a decrease in crystal quality.

[0005] Chinese patent CN106894090B discloses a method for preparing a high-quality, low-resistivity p-type SiC single crystal. The method grows a low-resistivity p-type SiC single crystal by doping B source and Al source in SiC powder. The method utilizes that both B and Al atoms occupy the position of Si atoms in SiC, but the radius of B atoms is smaller than that of Si atoms, while the radius of Al atoms is larger than that of Si atoms. By optimizing the specific doping concentrations of B and Al, the crystal stability and quality of the p-type SiC single crystal can be maintained. However, the B source is doped as an infinite source in SiC with low vapor pressure, and Al is doped as a finite source in SiC with high vapor pressure. The thermodynamic properties of the two doping sources are different, so it is difficult to accurately control the release matching degree in the same temperature field; in addition, the B source will introduce a deep energy level "D-Center" in the SiC single crystal, which is located at about 600meV at the top of the valence band, and will capture the holes ionized by the acceptor element, which is not conducive to reducing the p-type resistivity.

[0006] By doping N elements during the growth of p-type SiC single crystals, a single crystal type of heavily doped p-type SiC single crystal can be grown. This method uses the fact that N atoms occupying C lattice points will cause SiC unit cell shrinkage, which can compensate for the lattice expansion caused by Al doping to achieve the purpose of maintaining the stability of the heavily doped p-type SiC single crystal. However, since N introduces donor energy levels in SiC, its doping content needs to be accurately controlled: if the N doping amount is too low, the unit cell parameters cannot be maintained, and if the N doping amount is too high, the SiC conductivity type will be converted to n-type conductivity. At present, when growing Al-N dual-doped p-type SiC single crystals, a gas mass flowmeter is generally used to accurately control the N2 flow rate during its growth process to achieve the amount of N atoms doped. The common Al doping sources are solid substances such as Al, Al4C3, and Al2O3, and there is no corresponding gaseous doping source suitable for physical vapor transport method. The melting and boiling points of Al solid doping sources are much lower than the growth temperature of SiC single crystals, and its release is greatly affected by the temperature field. Therefore, the difficulty in matching the release of Al source and N source lies in how to control the release of Al source so that it can be synchronized with N doping. At present, a dual-coil heating method is generally used to achieve synchronous release of Al-N. Specifically, Al compounds with lower melting and boiling points are placed in a heating zone with lower temperature for high-temperature gasification, and SiC powder is placed in a high-temperature heating zone to achieve uniform Al doping during the growth process so that it can be doped synchronously with N. This method requires the equipment to be equipped with two independent heating systems to heat the SiC powder area and the doping source area separately to achieve different temperatures between the two. This method requires a high configuration of the heating system, and two controllers are required to control the induction coils respectively; at the same time, during the single crystal growth process, the "growth component backflow" phenomenon caused by the temperature gradient drive is very likely to occur, causing the crystal to grow reversely to the low-temperature Al source area, which is not conducive to the growth of p-type SiC single crystals. Summary of the invention

[0007] In order to solve the deficiencies of the prior art, the purpose of the present invention is to provide a heavily doped p-type SiC single crystal and its growth method and application. The present invention uses a compound or solid solution composed of aluminum and nitrogen elements as a type of doping source and other p-type doping sources as a type of doping source to perform Al-N co-doping. Furthermore, AlN material is placed in the SiC powder area as a type of doping source, so that when it decomposes, it provides Al atoms and N atoms in the same molar ratio, thereby achieving the simultaneous release of the N source and the Al source, which plays a role in maintaining the single crystal form of the heavily doped crystal; Al4C3, Al2O3, Al, etc. are placed as the second type of doping source to provide additional Al elements to achieve n[Al]:n[N] in the range of 1.2 to 3.0, ensuring that the grown crystal is a single crystal p-type SiC.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] In a first aspect, the present invention provides a method for growing a heavily doped p-type SiC single crystal, comprising the following steps:

[0010] S1. Place SiC powder in the SiC powder placement area at the bottom of the growth crucible; Mix a type I doping source and a type II doping source and place them at the center or edge of the SiC powder, wherein the molar ratio of aluminum atoms to nitrogen atoms in the mixed doping source is 1.2 to 3:1; Place a SiC seed crystal on the top of the crucible and tighten the crucible cover;

[0011] S2. Place the crucible in a single crystal growth furnace and evacuate the growth chamber; turn on the heating power supply, introduce protective gas, and grow the single crystal; after the growth is completed, introduce protective gas to atmospheric pressure and cool to room temperature to obtain a heavily doped p-type SiC single crystal.

[0012] In a second aspect, the present invention provides a heavily doped p-type SiC single crystal obtained by the growth method described in the first aspect.

[0013] In a third aspect, the present invention provides applications of the heavily doped p-type SiC single crystal described in the second aspect in the fields of aviation, aerospace exploration, new energy vehicles, 5G communications, smart grids, photovoltaic power generation, and high-power power electronic devices.

[0014] The beneficial effects achieved by one or more technical solutions of the present invention are as follows:

[0015] (1) The heavily doped p-type SiC single crystal growth method of the present invention uses AlN or the like as a type of doping source, thereby effectively avoiding the problem of the prior art that the Al source and the N source are difficult to synchronously and accurately control the doping during the SiC single crystal growth process. AlN can be cleverly decomposed into Al atoms and N atoms in equal molar ratios at high temperature, thereby ensuring that equal amounts of Al atoms and N atoms are decomposed in the SiC single crystal growth chamber, thereby effectively maintaining the crystal stability of the heavily doped SiC single crystal.

[0016] (2) The heavily doped p-type SiC single crystal growth method of the present invention can significantly increase the Al doping concentration in the p-type SiC single crystal by additionally adding two types of doping sources such as Al, Al4C3, and Al2O3, so that the doping molar ratio of the Al source and the N source satisfies: [n(Al atoms from the first type of doping source) + n(Al atoms from the second type of doping source)]: n(N atoms from the first type of doping source) is 1.2 to 3.0:1, thereby causing the acceptor energy level of the p-type SiC single crystal to hybridize, greatly reducing the acceptor ionization energy, and obtaining a low resistivity p-type SiC single crystal.

[0017] (3) The heavily doped p-type SiC single crystal growth method of the present invention uses solid doping sources as doping sources, which greatly reduces the dependence of doping of different substances on the temperature field, cleverly avoids the problem of different doping characteristics caused by differences in thermal properties between different doping sources, and lowers the technical threshold for p-type SiC single crystal growth.

[0018] (4) The doping method of the present invention does not require an extended crucible and a dual-zone heating system, and does not require improvement of the heating system of the single crystal growth equipment and the single crystal growth crucible structure. It has good compatibility with existing processes and is easy to promote and use.

[0019] (5) The co-doping scheme in the present invention is not only applicable to the growth of p-type SiC single crystals, but can also be applied to the growth of other single crystals that require co-doping or multi-doping to improve the quality of the single crystal, and can guide the growth of other heavily doped, high-quality crystals. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0021] Figure 1 The structure diagram of the crucible and heating system used in the present invention; wherein, 1: graphite insulation layer; 2: seed crystal; 3: heating coil; 4: type I doping source; 5: type II doping source; 6: graphite crucible; 7: SiC powder;

[0022] Figure 2 The secondary ion mass spectrometry test result of the p-type SiC substrate obtained by processing in Example 1 of the present invention;

[0023] Figure 3 This is the Raman mapping result of the p-type SiC substrate obtained by processing in Example 1 of the present invention;

[0024] Figure 4 This is the resistivity mapping result of the p-type SiC substrate obtained by processing in Example 1 of the present invention. DETAILED DESCRIPTION

[0025] A first typical embodiment of the present invention is a method for growing a heavily doped p-type SiC single crystal, comprising the following steps:

[0026] S1. Place SiC powder in the SiC powder placement area at the bottom of the growth crucible; Mix a type I doping source and a type II doping source and place them at the center or edge of the SiC powder, wherein the molar ratio of aluminum atoms to nitrogen atoms in the mixed doping source is 1.2 to 3:1; Place a SiC seed crystal on the top of the crucible and tighten the crucible cover;

[0027] S2. Place the crucible in a single crystal growth furnace and evacuate the growth chamber; turn on the heating power supply, introduce protective gas, and grow the single crystal; after the growth is completed, introduce protective gas to atmospheric pressure and cool to room temperature to obtain a heavily doped p-type SiC single crystal.

[0028] When n[Al]:n[N]<1.2:1.0, since the donor ionization energy of N atoms is much lower than the acceptor ionization energy of Al atoms, the resistivity of the grown crystal is high, and the crystal may even transform into n-type conductivity; when n[Al]:n[N]>3.0:1.0, the unit cell expansion caused by Al doping is much higher than the unit cell contraction caused by N doping. At this time, it is impossible to maintain the heavily doped p-type single crystal unit cell unchanged, and the grown crystal exhibits polymorphic symbiosis.

[0029] In one or more embodiments of this implementation, the first type of doping source is one or more compounds or solid solutions composed of aluminum and nitrogen elements, and the second type of doping source includes a single substance and one or more oxides, silicides, and carbides of p-type elements.

[0030] The first type of doping source can provide p-type atoms with controllable molar ratio and other atoms that maintain the p-type doped SiC unit cell parameters unchanged during the growth of SiC single crystal. The function of the first type of doping source is to maintain the stability of the SiC crystal while performing p-type doping on the SiC single crystal. The main function of the second type of doping source is to provide p-type doping atoms and increase the p-type atom doping concentration in the SiC single crystal.

[0031] In one or more embodiments of this implementation, the first type of doping source is AlN, and the particle size of the AlN is 3-20 mm. The purity of AlN should be above 99.9%, and no other impurities should be introduced. If the particle size is too small, AlN will decompose too quickly, which may cause concentrated doping of the doping source and deteriorate the crystal quality; if the particle size is too large, the decomposition rate of AlN will slow down, affecting the doping efficiency.

[0032] In one or more embodiments of this implementation, in step S1, when the particle size of one type of doping source is 10-20 mm, the mixed doping source is placed at the edge of the powder to promote decomposition; when the particle size of one type of doping source is 3-10 mm and less than 10 mm, the mixed doping source is placed in the center of the SiC powder to ensure stable release.

[0033] In one or more examples of this implementation mode, the second type of doping source is a single substance and one or more of oxides, silicides, and carbides of the Al element. The Al element with a shallow acceptor energy level is used as the doping source.

[0034] The doping concentration of p-type SiC single crystal can be controlled by controlling the loading amount, particle size, placement position, etc. of the doping source; when the particle size of the doping source is the same and the placement position is consistent, the more mass of the doping source loaded, the higher the doping concentration in the crystal; under the condition of maintaining the same loading amount of the doping source, the smaller the particle size of the doping source placed at the same position in the SiC powder area, the higher the doping concentration; under the condition of ensuring the same doping source mass and particle size, the closer the doping source is to the edge of the SiC powder, the higher the Al doping concentration in the crystal.

[0035] In one or more examples of this implementation mode, the distance between the surface of the SiC powder and the SiC seed crystal is 40-100 mm.

[0036] When the distance between the SiC powder surface and the SiC seed crystal exceeds 100 mm, the growth rate of the SiC single crystal slows down and the growth time is prolonged; when the distance between the SiC powder surface and the SiC seed crystal is less than 40 mm, the doping components and the SiC growth gas phase components cannot be evenly mixed when they are transmitted to the surface of the growth seed crystal.

[0037] In one or more embodiments of this implementation mode, the protective gas includes one or more of argon, helium, and hydrogen, the growth pressure of the single crystal growth is 20-50mbar, the upper cover temperature during the single crystal growth is 2000-2500℃, and the insulation time during the single crystal growth is 30-200h.

[0038] When the pressure is lower than 20 mbar, the decomposition rate of AlN is too fast, resulting in too fast release of Al source, which can easily cause defects such as grain boundaries and microtubes in the crystal; when the pressure is higher than 50 mbar, the axial ladder required for single crystal growth increases, the growth system needs to dissipate more heat, and the growth energy consumption will become higher.

[0039] A second typical embodiment of the present invention is a heavily doped p-type SiC single crystal obtained by the growth method described in the first typical embodiment.

[0040] In one or more examples of this implementation, the heavily doped p-type SiC single crystal includes one or more of 4H-SiC, 6H-SiC or 15R-SiC single crystal.

[0041] In one or more embodiments of this embodiment, the heavily doped p-type SiC single crystal has an Al doping concentration of not less than 7×10 19 cm -3 , resistivity not higher than 0.200Ω·cm, and half-peak width of rocking curve not exceeding 60 arc seconds.

[0042] A third typical embodiment of the present invention is the application of the heavily doped p-type SiC single crystal described in the second typical embodiment in the fields of aviation, aerospace exploration, new energy vehicles, 5G communications, smart grids, photovoltaic power generation, and high-power power electronic devices.

[0043] In order to enable those skilled in the art to more clearly understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below in combination with specific embodiments and comparative examples.

[0044] The crucible and heating system used in the present invention are as follows: Figure 1 As shown, SiC powder 7 is placed at the bottom of a graphite crucible 6, a type I doping source 4 and a type II doping source 5 are placed at the edge or center of the SiC powder 7, a seed crystal 2 is placed at the top of the graphite crucible 6, and the graphite crucible is placed in a heating system having a graphite insulation layer 1, and the heating system is heated by a heating coil 3. Figure 1 The first type doping source 4 and the second type doping source 5 are adjusted according to the actual situation. Figure 1 It is for illustration only and does not constitute an improper limitation of the present invention.

[0045] Example 1

[0046] A method for growing a heavily doped p-type SiC single crystal, comprising the following steps:

[0047] 10 g of AlN polycrystals with a particle size of 3 mm as a type one doping source and 1.8 g of Al4C3 as a type two doping source were weighed using a high-precision balance, so that the molar ratio of Al and N atoms in the SiC powder was n[Al]:n[N]=1.2, and the two were mixed evenly;

[0048] Place 2kg of SiC powder in the crucible, and place the mixed AlN and Al4C3 in the center of the SiC powder to slow down the release of the doping source;

[0049] Place a 4-inch 4H-SiC seed crystal on the top of the crucible, with the carbon surface as the growth surface, the distance between the SiC powder surface and the SiC seed crystal is 40 mm, and tighten the crucible cover;

[0050] The crucible is placed in a single crystal growth furnace, and the growth chamber is evacuated to below 0.1 Pa;

[0051] A protective gas of 50 sccm of Ar was introduced, and the heating power was turned on to set the crucible cover temperature at 2000°C and the pressure at 20 mbar, and the temperature was maintained for 300 hours for single crystal growth.

[0052] After the growth is completed, a protective gas is introduced to atmospheric pressure and the temperature is lowered to room temperature to obtain a 4-inch p-type 4H-SiC single crystal. The single crystal is cut, ground and polished to obtain a 4-inch p-type 4H-SiC substrate.

[0053] Test and characterize the p-type SiC substrate: Figure 2 As shown in the figure, the Al atomic doping concentration measured by secondary ion mass spectrometry is 8.7×10 19 cm -3 ; The HRXRD rocking curve test shows that the half-peak width of the diffraction peak of the p-type substrate is 21 arcsec, indicating that the crystal quality is good; Figure 3 As shown, the Raman mapping test shows that the 4H-SiC ratio of the p-type SiC substrate is 100%; the resistivity tester shows that the resistivity of the substrate is 0.124Ω·cm, as shown Figure 4 The test characterization results show that the prepared p-type SiC substrate has high crystal quality and stable crystal form.

[0054] Example 2

[0055] A method for growing a heavily doped p-type SiC single crystal, comprising the following steps:

[0056] 30 g of AlN single crystal with a particle size of 10 mm as a type I doping source and 74.6 g of Al2O3 as a type II doping source were weighed using a high-precision balance, so that the molar ratio of Al and N atoms in the SiC powder was n[Al]:n[N]=3.0, and the two were mixed evenly;

[0057] 3 kg of SiC powder was placed in the crucible, and the mixed AlN and Al4C3 were placed at the edge of the SiC powder to promote the release of the doping source;

[0058] Place an 8-inch 6H-SiC seed crystal on the top of the crucible, with the silicon surface as the growth surface, the distance between the SiC powder surface and the SiC seed crystal is 60 mm, and tighten the crucible cover;

[0059] The crucible is placed in a single crystal growth furnace, and the growth chamber is evacuated to below 0.1 Pa;

[0060] A protective gas of 200 sccm of Ar was introduced, and the heating power was turned on to set the crucible cover temperature at 2150°C and the pressure at 40 mbar. The temperature was maintained for 100 hours to grow single crystals.

[0061] After the growth is completed, protective gas is introduced to atmospheric pressure and the temperature is lowered to room temperature to obtain an 8-inch p-type 6H-SiC single crystal. The single crystal is cut, ground and polished to obtain an 8-inch p-type 6H-SiC substrate.

[0062] The p-type SiC substrate was tested and characterized. The Al atom doping concentration tested by secondary ion mass spectrometry was 5.2×10 20 cm -3 ; The half-peak width of the diffraction peak of the p-type substrate in the HRXRD rocking curve test is 24 arcsec, indicating that the crystal quality is good. The Raman mapping test shows that the 6H-SiC ratio of the p-type SiC substrate is 100%, and the resistivity tester shows that the resistivity of the substrate is 0.048Ω·cm. This shows that the prepared p-type SiC substrate has high quality. The substrate can be used to prepare high-power power electronic devices.

[0063] Example 3

[0064] A method for growing a heavily doped p-type SiC single crystal, comprising the following steps:

[0065] 100 g of AlN ceramic with a particle size of 20 mm as a type one doping source and 37.3 g of Al2O3 as a type two doping source were weighed using a high-precision balance, so that the molar ratio of Al and N atoms in the SiC powder was n[Al]:n[N]=1.3, and the two were mixed evenly;

[0066] 1 kg of SiC powder was placed in the crucible, and the mixed AlN and Al4C3 were placed at the edge of the SiC powder to promote the release of the doping source;

[0067] Place a 2-inch 15R-SiC seed crystal on the top of the crucible, with the silicon surface as the growth surface, the distance between the SiC powder surface and the SiC seed crystal is 100 mm, and tighten the crucible cover;

[0068] The crucible is placed in a single crystal growth furnace, and the growth chamber is evacuated to 0.01 Pa;

[0069] 800 sccm of Ar protective gas was introduced, and the heating power was turned on to set the crucible cover temperature at 2500°C and the pressure at 50 mbar, and the temperature was maintained for 30 hours for single crystal growth.

[0070] After the growth is completed, a protective gas is introduced to atmospheric pressure and the temperature is lowered to room temperature to obtain a 2-inch p-type 15R-SiC single crystal. The single crystal is cut, ground and polished to obtain a 2-inch p-type 15R-SiC substrate.

[0071] The p-type SiC substrate was tested and characterized. The Al atom doping concentration was 1.6×10 20 cm -3 ; The half-peak width of the diffraction peak of the p-type substrate tested by HRXRD is 45 arcsec, indicating that the crystal quality is good. The Raman mapping test shows that the 15R-SiC ratio of the p-type SiC substrate is 100%, and the resistivity tester shows that the resistivity of the substrate is 0.082Ω·cm. This shows that the prepared p-type SiC substrate has high quality and can be used for the preparation of high-power power electronic devices.

[0072] Comparative Example 1

[0073] The other conditions are the same as those in Example 1, except that the mass of the second type doping source of Al4C3 is 0.1 g, so that n[Al]:n[N] in the powder is less than 1.2:1. At this time, since the ionization energy of N atoms is much lower than that of Al atoms, the electron concentration in the crystal is higher than the hole concentration, and the conductivity type of the grown SiC is n-type rather than p-type, and the single crystal is unqualified.

[0074] Comparative Example 2

[0075] The other conditions are the same as those in Example 1, except that the mass of the second type of doping source of doped Al4C3 is 10g. At this time, n[Al]:n[N]>3.0:1 in the powder. At this time, the amount of N atoms provided by the first type of doping source is too low to maintain the unit cell expansion caused by excessive incorporation of Al atoms. The grown single crystals were tested and found to have multiple crystal forms such as 4H-SiC, 6H-SiC, and 15R-SiC, and a large number of defects such as microtubes were generated. The single crystals were unqualified and could not be used for the preparation of high-power devices.

[0076] Comparative Example 3

[0077] The other conditions are the same as those in Example 1, except that no type I doping source is placed in the SiC powder, and 5 sccm of N2 is introduced at the same time as 50 sccm of Ar is introduced during the single crystal growth process. N2 can provide a stable N source and can be precisely controlled using a gas mass flowmeter, while the release of the type II doping source Al4C3 varies with the temperature field, making it difficult to achieve precise synchronous release of the Al source and the N source. As a result, the type II doping source releases the Al source in a concentrated manner in the early growth stage, and polytypes are generated in the crystal with n[Al]:n[N]>3.0:1, inducing microtubes; and in the later growth stage, n[Al]:n[N]<1.2:1, and the crystal transforms into n-type conductivity. The single crystal prepared in this comparative example is unqualified and cannot be used for the preparation of high-power devices.

[0078] Comparative Example 4

[0079] The other conditions are the same as those in Example 1, except that the growth pressure is 1 mbar, so that the AlN in the SiC powder decomposes rapidly under low pressure, resulting in a sudden increase in the Al doping concentration at the initial stage of crystal growth and nucleation, and a large number of grain boundaries appear at the growth interface in the nucleation stage, resulting in poor quality of the prepared crystal. The HRXRD rocking curve test of the obtained p-type SiC substrate crystal form shows that the diffraction peak has a half-peak width of 120 arc seconds, and there are two crystal forms of 4H-SiC and 6H-SiC. The prepared crystal cannot be used for the preparation of high-power power electronic devices.

[0080] Comparative Example 5

[0081] The other conditions are the same as those in Example 1, except that the growth pressure is 100 mbar. At this time, in order to ensure that the single crystal growth has a suitable growth rate, the insulation structure needs to be changed to obtain a large growth axis ladder. At this time, the single crystal growth is not only far away from the equilibrium state, deteriorating the crystal quality, but also leading to increased growth power consumption. The HRXRD rocking curve test of the obtained p-type SiC substrate crystal form shows that the half-peak width of the diffraction peak is 158 arc seconds, indicating that the crystal quality is poor and the prepared crystal cannot be used for the preparation of high-power power electronic devices.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for growing a heavily doped p-type SiC single crystal, characterized in that: The following steps are involved: S1. Place SiC powder in the SiC powder placement area at the bottom of the growth crucible; Mix a type I doping source and a type II doping source and place them at the center or edge of the SiC powder, wherein the molar ratio of aluminum atoms to nitrogen atoms in the mixed doping source is 1.2-3:1; Place a SiC seed crystal on the top of the crucible and tighten the crucible cover; S2, placing the crucible in a single crystal growth furnace, evacuating the growth chamber; turning on the heating power supply, introducing a protective gas, and growing the single crystal; after the growth is completed, introducing a protective gas to atmospheric pressure, cooling to room temperature, and obtaining a heavily doped p-type SiC single crystal; The first type of doping source is AlN, and the second type of doping source is one or more of Al, Al4C3, and Al2O3.

2. The growth method according to claim 1, characterized in that The particle size of the AlN is 3-20 mm.

3. The growth method according to claim 1, characterized in that In step S1, when the particle size of one type of doping source is 10-20 mm, the mixed doping source is placed at the edge of the powder to promote decomposition; when the particle size of one type of doping source is 3-10 mm and less than 10 mm, the mixed doping source is placed in the center of the SiC powder to ensure stable release.

4. The growth method according to claim 1, characterized in that The distance between the surface of SiC powder and SiC seed crystal is 40-100 mm.

5. The growth method according to claim 1, characterized in that The protective gas is one or more of argon, helium, and hydrogen. The growth pressure of the single crystal is 20-50 mbar. The upper cover temperature is 2000-2500°C during the single crystal growth. The insulation time is 30-200 h during the single crystal growth.

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