A nitride epitaxial wafer, its preparation method and application

Abstract

This invention provides a nitride epitaxial wafer, its preparation method, and its applications. The method includes: sequentially preparing an N-type nitride layer and an active layer on a substrate; growing a p-type nitride front layer on the active layer under conditions of introducing a surfactant containing active elements; the p-type nitride front layer containing different active elements, first and second dopant elements; depositing an atomic deposition layer containing the first and second dopant elements on the p-type nitride front layer after stopping the introduction of the surfactant; growing a p-type nitride back layer containing the first dopant element on the atomic deposition layer; and performing heat treatment to desorb the active elements in the p-type nitride front layer and to allow the first and second dopant elements in the atomic deposition layer to migrate into the p-type nitride front and back layers, respectively. This invention utilizes the desorption of active elements and diffusion in the atomic deposition layer to increase the hole concentration of the p-type nitride layer, improve the brightness of the nitride epitaxial wafer, and reduce the operating voltage and droop effect.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, specifically relating to a nitride epitaxial wafer, its preparation method, and its application. Background Technology

[0002] In recent years, significant progress has been made in the research of nitride-based devices, but many challenges remain. Low-resistivity p-type doping is a major obstacle hindering the widespread application of nitride materials (such as GaN). Currently, LEDs entering the large-scale market and HBT devices with enormous research and application potential both require excellent low-resistivity, high-hole-concentration p-type-doped nitride materials. Therefore, the development progress of p-type nitride materials directly affects the application of LEDs, HBTs, and other related devices. Currently, Mg is the main p-type dopant, but its activation efficiency is typically less than 1%, and the Mg-H passivation effect is one of the factors restricting the development of nitride-based devices. Furthermore, the presence of Al components in the nitride increases the acceptor ionization energy, further complicating the achievement of high carrier concentration and high mobility. Furthermore, since electrons have a faster mobility than holes and the concentration of free electrons is higher than that of holes, the distribution of electrons and holes in the active layer is uneven. Holes are concentrated in the active layer closer to the p-type nitride layer and gradually decay towards the N-type nitride layer, which is not conducive to the recombination of electrons and holes.

[0003] It is evident that improving the doping efficiency of p-type nitride materials is of great significance for the application of nitride materials, and there is an urgent need to propose a p-type nitride and semiconductor device with high hole concentration. Summary of the Invention

[0004] To solve all or part of the above-mentioned technical problems, the present invention provides the following solutions:

[0005] A method for preparing a nitride epitaxial wafer, characterized by comprising:

[0006] S1. An N-type nitride layer and an active layer are sequentially prepared on the substrate;

[0007] S2. Under the condition of introducing a surfactant, a p-type nitride front layer is grown on the active layer; wherein the surfactant contains an active element, and the p-type nitride front layer contains the active element, a first dopant element, and a second dopant element, and the active element, the first dopant element, and the second dopant element are all different.

[0008] S3. With the surfactant supply stopped, an atomic deposition layer is deposited on the p-type nitride front layer; wherein the atomic deposition layer comprises the first dopant element and the second dopant element;

[0009] S4. A p-type nitride back layer with the first doped element is grown on the atomic deposition layer;

[0010] S5. Perform a first heat treatment on the structure obtained in step S4 to desorb the active element in the p-type nitride front layer and to allow the first dopant element and the second dopant element in the atomic deposition layer to migrate into the p-type nitride front layer and the p-type nitride back layer, respectively.

[0011] S6. Repeat S2-S5 at least once to obtain a p-type nitride layer.

[0012] The preparation method provided by this invention utilizes the desorption of active elements and the diffusion effect of atomic deposition layers to improve the effective doping concentration and incorporation efficiency of dopants in p-type nitride layers. After desorption, active elements generate bonding vacancies in the p-type nitride front layer. The first and second dopants in the atomic deposition layer diffuse, with the first dopant diffusing into the p-type nitride front layer to occupy the bonding vacancies formed by In desorption, thereby increasing the effective doping concentration of the first dopant in the front layer. Furthermore, since the p-type nitride front layer contains a co-doped second dopant, this increases the potential energy for the second dopant in the atomic deposition layer to diffuse into the p-type nitride front layer. Therefore, the second dopant in the atomic deposition layer is more likely to diffuse into the p-type nitride back layer, thus forming a p-type nitride back layer that is also co-doped with the first and second dopants.

[0013] When the first dopant element is an acceptor impurity, it can effectively increase the hole concentration in the p-type nitride layer, providing a high-concentration hole injection for the nitride epitaxial wafer, balancing the electron injection balance between the n-type nitride layer and the hole injection balance between the p-type nitride layer, improving the brightness of the nitride semiconductor light-emitting structure, reducing the operating voltage, and reducing the droop effect (i.e., the phenomenon of reduced luminous efficiency as the current increases) that occurs in the nitride epitaxial wafer with increasing injection current. It is suitable for high-current operating conditions and meets the application requirements of high-power epitaxial wafers.

[0014] In some embodiments, the first dopant element is Mg, the second dopant element is Si, the surfactant is In surfactant, and the active element is In. This method can increase the effective doping concentration and incorporation efficiency of Mg in the p-type nitride layer, thereby increasing the hole concentration. Compared to conventional in-situ Mg doping, this method increases the effective doping concentration of Mg in the p-type nitride front layer through Mg diffusion, avoiding the increased defects and donor self-compensation effect in the grown p-type nitride under high-dose doping conditions. Furthermore, because the formation energy of Si in the atomic deposition layer is low in the nitride, it can suppress the diffusion of Mg atoms into the p-type nitride front layer before In desorption, avoiding the formation of Mg interstitial atom impurities that would cause light absorption. This is because before In atom desorption, Mg diffuses into the p-type nitride front layer as interstitial impurity atoms.

[0015] The In surfactant can be any one or a combination of two or more of the conventional In surfactants in the art, such as trimethylindium, triethylindium, and dimethylethylindium, but is not limited thereto.

[0016] In some embodiments, the p-type nitride front layer includes a first sublayer and a second sublayer sequentially stacked on the active layer, and step S2 specifically includes:

[0017] S21. The surfactant is introduced at a first flow rate to grow the first sublayer;

[0018] S22. The surfactant is introduced at a second flow rate to grow the second sublayer on the first sublayer;

[0019] S23. Repeat S21-S22 for the first preset number of times;

[0020] Wherein, the first flow rate is less than the second flow rate.

[0021] The method described above circulates the surfactant at a lower first flow rate and a higher second flow rate. On the one hand, this ensures sufficient surfactant supply while preventing lattice stress distortion in the first sublayer due to the incorporation of active elements, thus avoiding defect-induced light absorption and leakage channels. On the other hand, the first sublayer formed with a relatively low first flow rate can serve as a growth template for the second sublayer, increasing surfactant incorporation and providing more diffusion centers. Furthermore, directly introducing the surfactant at a high flow rate would lead to large lattice distortion and uneven composition distribution; therefore, this method also improves dopant diffusion uniformity and enhances carrier expansion capability within the second sublayer.

[0022] In some preferred embodiments, the flow ratio of the first flow to the second flow is 1:20 to 1:5.

[0023] In some preferred embodiments, the first flow rate is 50-200 sccm, and the second flow rate is 500-1000 sccm.

[0024] In some embodiments, the first preset number of times is 2 to 5 times.

[0025] In some embodiments, the thickness of the first sublayer is 3-15 nm, and the Mg doping concentration of the first sublayer is 2 × 10⁻⁶. 19 -2×10 20 cm -3 The Si doping concentration of the first sublayer is 1×10⁻⁶. 17 -5×10 18 cm -3 .

[0026] In some embodiments, the thickness of the second sublayer is 2-5 nm, and the Mg doping concentration of the second sublayer is 2 × 10⁻⁶. 19 -2×10 20 cm -3 The Si doping concentration of the second sublayer is 1×10⁻⁶. 17 -5×10 18 cm -3 .

[0027] In some embodiments, step S3 specifically includes:

[0028] S31. Stop the flow of the surfactant, and under the condition of the flow of the first doping element source and the second doping element source, perform a second heat treatment for a first set time to form the atomic deposition layer.

[0029] S32. Stop the flow of the surfactant, the first dopant source and the second dopant source, and perform a third heat treatment for a second set time;

[0030] S33, Repeat S31-S32 for the second preset number of times.

[0031] The second heat treatment performed in step S32 can promote the full migration of the first dopant element and the second dopant element, and avoid atomic aggregation.

[0032] In some embodiments, the first set time is 5 to 60 seconds.

[0033] In some embodiments, the second set time is 5 to 30 seconds.

[0034] In some embodiments, the thickness of the atomic deposition layer is 1~5 nm.

[0035] In some embodiments, the second preset number of times is 3 to 14 times.

[0036] In some embodiments, the temperatures of steps S2, S3, S4, and S5 are set to T respectively. a T b T c T d , among which, T a <T b T b ≤T c T c <T d During the preparation process, T a Heat up to T b T b Heat up to T c T cHeat up to T d A linear heating method is employed, with a heating rate of 0.2~1℃ / s. This relatively low-rate linear change effectively anneales the nitride epitaxial wafer, allowing for the effective release of internal stress, improving the uniformity of composition distribution, and preventing uneven composition distribution caused by localized stress accumulation within the epitaxial nitride wafer due to sudden temperature changes.

[0037] In some embodiments, the growth of the p-type nitride front layer includes: introducing an In surfactant at a temperature of 700-800°C and a pressure of 300-600 torr to grow a thickness of 5-20 nm and a Mg doping concentration of 2 × 10⁻⁶. 19 -2×10 20 cm -3 The Si doping concentration is 1×10 17 -5×10 18 cm -3 The p-type nitride front layer.

[0038] Growing the p-type nitride front layer within this relatively low growth temperature range can enhance the incorporation of In surfactants into the p-type nitride front layer, thereby increasing In bonding occupancy. After sufficient migration of Mg and Si in the atomic deposition layer, the effective doping concentration of Mg in the p-type nitride front layer is increased, which can increase the carrier concentration by an order of magnitude, reaching 1×10⁻⁶ in some embodiments. 18 cm -3 above.

[0039] In some embodiments, the deposition of the atomic deposition layer includes: stopping the introduction of In surfactant and introducing Mg source and Si source for surface heat treatment for 10-90s under conditions of temperature of 750-850℃ and pressure of 100-400 torr.

[0040] The Mg source and Si source used can be any one or more combinations of conventional Mg sources and Si sources in the art, and the present invention does not impose any particular limitation on them. For example, the Mg source can be magnesia-ceramic (Cp2Mg), (MCp)2Mg, etc., and the Si source can be SiH4, SiH2Cl2, SiHCl3, SICl4, etc.

[0041] In some embodiments, the growth of the p-type nitride back layer includes: growing a thickness of 5-20 nm and a Mg doping concentration of 2×10⁻⁶ under conditions of a temperature of 750-850°C and a pressure of 200-600 torr. 19 -2×10 20 cm -3 The p-type nitride back layer.

[0042] Growing the back layer within this relatively high growth temperature range can reduce defects in p-type nitrides, improve the crystal quality of the p-type nitride back layer, and interrupt dislocation propagation. After sufficient Si migration in the atomic deposition layer, the p-type nitride back layer also exhibits Si doping. Because epitaxial growth is inherently a non-equilibrium growth process, compared to the in-situ Si co-doping process for the p-type nitride back layer, the method of this invention can effectively prevent Si atoms from forming interstitial impurities in the p-type nitride back layer, thus avoiding light absorption and the formation of leakage channels due to the aggregation of Si interstitial impurities. Furthermore, utilizing the low formation energy of Si atoms, the first heat treatment can effectively occupy defect centers, thereby increasing the formation energy of donor defects in the p-type nitride back layer, reducing donor compensation, and thus improving the doping efficiency of the p-type nitride back layer.

[0043] In some embodiments, step S5 includes: introducing a nitrogen source to perform the first heat treatment at a temperature of 900-1000°C and a pressure of 100-300 torr.

[0044] In some embodiments, the first heat treatment causes the atomic deposition layer to diffuse completely, forming a p-type nitride layer consisting of a p-type nitride front layer and a p-type nitride back layer after sufficient migration of the first and second doped element atoms. If the atomic deposition layer does not diffuse completely, atomic deposition layers remain in the final p-type nitride layer, causing the residual atoms to act as impurities and absorb light, reducing brightness and light extraction efficiency.

[0045] In some embodiments, step S6 includes repeating S2-S5 2-6 times.

[0046] In some embodiments, the total thickness of the p-type nitride layer is 90-240 nm.

[0047] The material of the p-type nitride layer includes one or more of GaN, AlN, AlGaN, InN, InGaN, AlInN, and AlInGaN, but is not limited to these.

[0048] In some embodiments, the growth of the N-type nitride layer includes: growing a thickness of 1-5 μm and a Si doping concentration of 1×10⁻⁶ under conditions of a temperature of 1050-1250°C and a pressure of 100-300 torr. 18 -1×10 19 cm -3 The N-type nitride layer.

[0049] In some embodiments, the thickness of the N-type nitride layer is 1-5 μm.

[0050] In some embodiments, the active layer includes a plurality of light-emitting units arranged sequentially along a direction away from the N-type nitride layer, and the growth of the light-emitting units includes:

[0051] Quantum well layers with a thickness of 1-5 nm are grown under conditions of temperature 650-850℃ and pressure 100-400 torr.

[0052] A quantum barrier layer with a thickness of 6-25 nm is grown on the quantum well layer under conditions of temperature of 700-950℃ and pressure of 100-400 torr.

[0053] In some embodiments, the substrate material includes sapphire, silicon, silicon carbide, and GaN, but is not limited to these.

[0054] In some embodiments, the material of the nitride epitaxial wafer can be one of GaN, AlN, AlGaN, InN, InGaN, AlInN, and AlInGaN.

[0055] The second objective of this invention is to provide a nitride epitaxial wafer, which is prepared by the method described in any of the above technical solutions.

[0056] When the first dopant element is Mg and the second dopant element is Si, it not only improves the doping incorporation efficiency of Mg in the p-type nitride layer and increases the hole concentration, forming a Mg and Si co-doped p-type nitride layer; but also, when Si is incorporated into the p-type nitride layer as a co-doping atom, the nitride Fermi level increases, which increases the donor defect formation energy and further reduces the donor compensation; at the same time, the ionization energy in the acceptor-donor-acceptor complex formed in the p-type nitride front layer decreases, reducing the acceptor formation energy; and the short-range bipolar scattering of carriers in the complex increases the carrier mobility, thereby obtaining a p-type nitride layer with high hole concentration and high mobility.

[0057] A third objective of this invention is to provide a semiconductor device comprising the aforementioned nitride epitaxial wafer.

[0058] Compared with the prior art, the present invention has at least the following beneficial effects:

[0059] (1) The preparation method provided by the present invention utilizes the desorption of active elements and the diffusion of atomic deposition layers to improve the effective doping efficiency of doped elements in the p-type nitride layer. Compared with the conventional in-situ doping process in the prior art, this method can effectively improve the defects and donor self-compensation effect in the p-type nitride layer grown under high-dose doping process conditions, increase the hole concentration in the p-type nitride, and improve the conductivity.

[0060] (2) The preparation method provided by the present invention can improve the hole injection concentration of the nitride epitaxial wafer, balance the electron injection balance of the n-type nitride layer and the hole injection balance of the p-type nitride layer, improve the brightness of the nitride epitaxial wafer, reduce the working voltage, and reduce the droop effect of the nitride epitaxial wafer as the injection current increases. It is suitable for working under high current conditions and meets the application requirements of high power epitaxial wafers.

[0061] Instruction manual illustrations

[0062] Figure 1 This is a schematic flowchart of the method for preparing nitride epitaxial wafers provided by the present invention;

[0063] Figure 2 This is a schematic diagram of the structure of the nitride epitaxial wafer provided by the present invention;

[0064] Figure 3 This is a schematic diagram of the structure of the p-type GaN front layer provided by the present invention.

[0065] 100 - Substrate, 200 - N-type nitride layer, 300 - Active layer, 400 - p-type nitride layer, 401 - p-type nitride front layer, 4011 - First sublayer, 4012 - Second sublayer, 402 - p-type nitride back layer. Detailed Implementation

[0066] The technical solutions of the present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of the present invention. The specific functional details disclosed herein should not be construed as limiting, but are merely intended to form the basis of the claims and to teach those skilled in the art to employ the representative basis of the invention in different ways in any suitable detailed embodiment.

[0067] Please see Figure 1 , Figure 1 This is a schematic flowchart of the method for preparing nitride epitaxial wafers provided by the present invention, the method comprising:

[0068] S1. An N-type nitride layer and an active layer are sequentially prepared on the substrate.

[0069] The substrate serves as the support for the growth of the nitride epitaxial wafer, and the N-type nitride layer acts as the injection layer for charge carriers (electrons) in the active layer. The following schemes can be adopted:

[0070] S11. Under conditions of temperature 1050-1250℃ and pressure 100-300 torr, grow a Si doping concentration of 1×10⁻⁵ μm on a substrate. 18 -1×10 19 cm -3 The N-type nitride layer.

[0071] S12. An active layer is grown on the N-type nitride layer.

[0072] The active layer serves as the active region of the nitride epitaxial wafer, where carriers recombine to emit light. The active layer comprises 2-15 light-emitting units arranged sequentially along a direction away from the N-type nitride layer. Each light-emitting unit includes a quantum well layer and a quantum barrier layer arranged sequentially along a direction away from the N-type nitride layer. The growth of the light-emitting units includes:

[0073] S121. Under conditions of temperature of 650-850℃ and pressure of 100-400 torr, a quantum well layer with a thickness of 1-5 nm is grown.

[0074] S122. Under conditions of temperature of 700-950℃ and pressure of 100-400 torr, a quantum barrier layer with a thickness of 6-25 nm is grown on the quantum well layer.

[0075] S2. Under the condition of introducing surfactant, a p-type nitride front layer is grown on the active layer.

[0076] Surfactants contain active elements, and the p-type nitride front layer contains active elements, a first dopant element, and a second dopant element, each of which is different.

[0077] Furthermore, the first doping element can be Mg, the second doping element can be Si, the surfactant can be In, and the active element can be In.

[0078] In one embodiment, the growth of the p-type nitride front layer includes: introducing an In surfactant at a temperature of 700-800°C and a pressure of 300-600 torr to grow a thickness of 5-20 nm and a Mg doping concentration of 2 × 10⁻⁶. 19 -2×10 20 cm -3 The Si doping concentration is 1×10 17 -5×10 18 cm -3 The p-type nitride front layer.

[0079] In Si-Mg co-doped p-type nitride front layers, Si, as a co-doping atom, increases the Fermi level of the nitride, increases the donor defect formation energy, and reduces donor compensation. Simultaneously, the ionization energy of the acceptor-donor-acceptor complex formed in the p-type nitride front layer decreases, reducing the acceptor formation energy; furthermore, short-range bipolar scattering of carriers in the complex enhances carrier mobility, thus enabling the acquisition of p-type nitride front layers with high hole concentration and high mobility.

[0080] The p-type nitride prelayer grows in a relatively low temperature range (700-800℃), which can improve the incorporation efficiency of surfactants and increase the bonding site occupancy of active elements in the p-type nitride prelayer.

[0081] The aforementioned p-type nitride front layer growth can obtain a p-type nitride front layer with highly active element bonding sites. However, through systematic research in this invention, it has been found that during the p-type nitride front layer growth process, alternating between low and high flow rates of the In surfactant can further reduce defects caused by lattice stress distortion while increasing the incorporation of the In surfactant.

[0082] In another embodiment, the p-type nitride front layer includes a first sublayer and a second sublayer sequentially stacked on the active layer, and step S2 specifically includes:

[0083] S21. The surfactant is introduced at the first flow rate to grow the first sublayer.

[0084] Under conditions of 700-800℃ and 300-600 torr, an In surfactant with a flow rate of 50-200 sccm is introduced to grow a thickness of 3-15 nm and a Mg doping concentration of 2×10⁻⁶. 19 -2×10 20 cm -3 The Si doping concentration is 1×10 17 -5×10 18 cm -3 The first sub-layer.

[0085] Using In surfactants can improve the doping efficiency of Mg doping.

[0086] S22. A surfactant is introduced at a second flow rate to grow a second sublayer on the first sublayer.

[0087] Under conditions of 700-800℃ and 300-600 torr, an In surfactant with a flow rate of 500-1000 sccm is introduced to grow a thickness of 2-5 nm with a Mg doping concentration of 2×10⁻⁶. 19 -2×10 20 cm -3 The Si doping concentration is 1×10 17 -5×10 18 cm -3 The second sub-layer.

[0088] Growing the second sublayer at a relatively low growth temperature enhances the incorporation of In surfactants into the p-type nitride prelayer, and synergistically, the introduction of high flow rates of In surfactants improves bonding site occupancy.

[0089] S23, repeat S21-S22 2-5 times.

[0090] S3. With the surfactant supply stopped, deposit an atomic deposition layer on the p-type nitride front layer.

[0091] The atomic deposition layer contains a first doping element and a second doping element.

[0092] In one embodiment, under conditions of 750-850°C and 100-400 torr, the flow of In surfactant can be stopped, and Mg source and Si source can be introduced for surface heat treatment for 10-90s to form an atomic deposition layer with a thickness of 1-5nm.

[0093] Although the above methods can form a MgSi atom deposition layer, MgSi atom aggregation is prone to occur. This invention improves the MgSi atom aggregation effect by alternating between heat treatment under conditions of introducing dopant element sources (including a first dopant element source and a second dopant element source) and heat treatment under conditions of not introducing dopant element sources. Specifically, step S3 includes:

[0094] S31. When the temperature increases linearly to 750-850℃, stop the flow of surfactant, and perform a second heat treatment for 5-60s while introducing the first dopant source and the second dopant source.

[0095] The first doping element source can be a Mg source, and the second doping element source can be a Si source. Through the process in step S31, a MgSi deposition layer can be formed.

[0096] S32. Under the condition that the temperature increases linearly to 750-850℃, stop the flow of surfactant, first dopant source and second dopant source, and perform third heat treatment for 5~30s.

[0097] The process in step S32 allows MgSi atoms to migrate fully, preventing MgSi atoms from accumulating.

[0098] S33, repeat S31-S32 3-14 times.

[0099] In some embodiments of the present invention, the atomic deposition layer is configured to simultaneously contain Mg and Si atoms. This not only promotes the simultaneous diffusion of Mg and Si atoms but also prevents the formation of Mg interstitial atom impurities. Because the formation energy of Si atoms in the atomic deposition layer is low within the nitride, it can suppress the diffusion of Mg atoms into the p-type nitride front layer before In desorption, thus avoiding light absorption caused by the formation of Mg interstitial atom impurities. This is because before In atom desorption, Mg diffuses into the p-type nitride front layer and forms as interstitial impurity atoms.

[0100] The second doping element can also be O or C, but due to the high technical difficulty of forming Mg, O atomic deposition layers or Mg, C atomic deposition layers, and the fact that the effect is not better than MgSi atomic deposition layers, MgSi atomic deposition layers are the preferred option.

[0101] The first heat treatment preferably ensures complete diffusion of the atomic deposition layer, meaning that the final p-type nitride layer does not contain any atomic deposition layer. This is because incomplete diffusion of the atomic deposition layer can lead to residual atoms acting as impurities, causing light absorption and reducing brightness and light extraction efficiency.

[0102] S4: A p-type nitride back layer with the first doped element is grown on the atomic deposition layer.

[0103] Under conditions of 750-850℃ and 200-600 torr, a growth thickness of 5-20 nm and a Mg doping concentration of 2×10⁻⁶ were achieved. 19 -2×10 20 cm -3 The p-type nitride back layer.

[0104] Growing p-type nitride back layers at relatively high growth temperatures (750-850℃) can reduce defects in p-type nitrides, improve the crystal quality of p-type nitride back layers, and interrupt dislocation propagation.

[0105] The p-type nitride back layer grown in step S4 is, for example, a single Mg-doped p-type nitride back layer. That is, the incorporation of Si atoms in the p-type nitride back layer is achieved entirely through the migration of Si atoms in the atomic deposition layer. This can prevent co-doped Si atoms from aggregating in the p-type nitride back layer to form leakage channels, blocking the connection between the leakage channels and the light-emitting layer, thereby improving leakage performance.

[0106] S5: Perform a first heat treatment on the structure obtained in step S4 to desorb the active elements in the p-type nitride front layer and to allow the first and second doped elements in the atomic deposition layer to migrate into the p-type nitride front layer and the p-type nitride back layer, respectively.

[0107] The first heat treatment is carried out by introducing a nitrogen source at a temperature of 900-1000℃ and a pressure of 100-300 torr.

[0108] The first heat treatment at a relatively high temperature (900-1000℃) enables the In active element to break bonds in the p-type nitride front lattice, resulting in desorption and detachment from the p-type nitride front surface. Simultaneously, Mg and Si atoms diffuse into the MgSi atom deposition layer. Since Si exists as a co-doped atom in the p-type nitride front layer, the co-doped Si atoms increase the potential energy for Si atoms in the MgSi atom deposition layer to diffuse into the p-type nitride front layer, making it easier for Si atoms in the MgSi atom deposition layer to diffuse into the p-type nitride back layer. Meanwhile, Mg atoms in the MgSi atom deposition layer occupy the bonding vacancies formed by In desorption, forming Mg doped atoms in the p-type nitride front layer, thereby improving the Mg doping incorporation efficiency. Compared to conventional in-situ Mg doping processes, this method avoids the high defect rate and donor self-compensation effect in p-type nitride layers grown under high-dose doping conditions, thus increasing the hole concentration.

[0109] S6: Repeat S2-S5 at least once to obtain a p-type nitride layer with a thickness of 20-200 nm.

[0110] The number of repetitions for S2-S5 can be set according to specific application needs, such as 1 time, 2 times or more, for example, 2-6 times.

[0111] Please see Figure 2 , Figure 2 This is a structural diagram of the nitride epitaxial wafer provided by the present invention. The nitride epitaxial wafer is prepared by the above-described method and includes a substrate 100, an N-type nitride layer 200, an active layer 300, and a p-type nitride layer 400 stacked together. The p-type nitride layer 400 includes at least one p-type nitride unit stacked on the active layer 300. Each p-type nitride unit includes a p-type nitride front layer 401 and a p-type nitride back layer 402 stacked on the active layer.

[0112] Furthermore, such as Figure 3 As shown, the p-type nitride front layer 401 includes at least one front layer structure stacked on the active layer 300, and the front layer structure includes a first sublayer 4011 and a second sublayer 4012 stacked on the active layer 300.

[0113] The present invention also provides a semiconductor device comprising the above-described nitride epitaxial wafer.

[0114] Example 1

[0115] This embodiment provides a method for preparing a nitride epitaxial wafer, which specifically includes the following steps:

[0116] (1) Place the sapphire substrate into the growth chamber of the metal-organic chemical vapor deposition (MOCVD) system.

[0117] (2) Under the conditions of 1150℃ and 200 torr, the growth thickness is 3μm and the Si doping concentration is 5×10⁻⁶. 18 cm -3 The material is an N-type nitride layer of gallium nitride (denoted as n-type GaN layer).

[0118] (3) Growing an active layer on an n-type GaN layer, including the following steps:

[0119] S31: Adjust the temperature to 750℃ and the pressure to 250 torr to grow a quantum well layer (denoted as InGaN quantum well layer) with a thickness of 3nm on the n-type GaN layer.

[0120] S32: Raise the temperature to 825℃ to grow a 15.5nm thick GaN quantum barrier layer (denoted as GaN quantum barrier layer) on the InGaN quantum well layer to form a light-emitting unit.

[0121] S33: Repeat S31-S32 5 times to form an active layer with 5 light-emitting units.

[0122] (4) Growing a p-type nitride front layer on the active layer, including the following steps:

[0123] S41: Adjust the temperature to 750℃ and the pressure to 400 torr. First, introduce trimethylindium (TMIn) into the growth chamber at a flow rate of 150 sccm. The growth thickness is 5 nm, and the Mg doping concentration is 1×10⁻⁶. 20 cm -3 The Si doping concentration is 1×10 18 cm -3 The first sub-layer.

[0124] S42: Adjust the TMIn flow rate to 800 sccm, grow a thickness of 3 nm, and set the Mg doping concentration to 1×10⁻⁶. 20 cm -3 The Si doping concentration is 1×10 18 cm -3 The second sub-layer.

[0125] S43: Repeat S41-S42 5 times to form a p-type nitride front layer (denoted as p-type GaN front layer) with a thickness of 40nm and made of gallium nitride.

[0126] (5) Depositing an atomic deposition layer containing Si and Mg (denoted as MgSi atomic deposition layer) on the p-type GaN front layer includes the following steps:

[0127] S51: Stop the flow of TMIn, linearly increase the temperature to 800℃ at a heating rate of 0.3℃ / s, adjust the pressure to 250 torr, introduce Cp2Mg at a flow rate of 1000 sccm and SiH4 at a flow rate of 300 sccm, perform surface MgSi heat treatment on the p-type GaN front layer and maintain it for 30s to obtain a MgSi atomic deposition layer.

[0128] S52: Interrupt the introduction of Cp2Mg and SiH4, and continue heat treatment for 15s to promote the full migration of Mg and Si atoms.

[0129] S53: Repeat S51-S52 8 times alternately to form a MgSi atomic deposition layer with a thickness of 3nm.

[0130] (6) The temperature was increased to 820℃ at a heating rate of 0.3℃ / s, and the pressure was adjusted to 400 torr. The growth thickness was 15nm and the Mg doping concentration was 1×10⁻⁶. 20 cm -3 The material is a p-type nitride back layer of GaN (denoted as p-type GaN back layer).

[0131] (7) Increase the temperature to 950℃ at a heating rate of 0.8℃ / s, adjust the pressure to 250 torr, and introduce NH3 with a flow rate of 60slm for N heat treatment.

[0132] During the N heat treatment, In in the p-type GaN front layer desorbs, and the MgSi atom deposition layer diffuses, with Mg atoms diffusing into the p-type GaN front layer to occupy the bonding vacancies formed by In desorption, thereby improving the Mg doping incorporation efficiency of the p-type GaN front layer; and Si atoms in the MgSi atom deposition layer diffuse into the p-type GaN back layer, transforming the single Mg-doped p-type GaN back layer into a Mg and Si co-doped p-type GaN back layer; after the MgSi atom deposition layer has completely diffused, the N heat treatment is stopped, forming a Mg and Si co-doped p-type GaN layer composed of the p-type GaN front layer and the p-type GaN back layer.

[0133] (8) Repeat steps (4) to (7) twice until a p-type nitride layer with a thickness of 110 nm and a material of GaN is formed (denoted as p-type GaN layer), thereby obtaining a nitride epitaxial wafer.

[0134] Example 2

[0135] This embodiment provides a method for preparing a nitride epitaxial wafer, which specifically includes the following steps:

[0136] (1) Place the sapphire substrate into the growth chamber of the organometallic chemical vapor deposition system.

[0137] (2) Under the conditions of temperature of 1050℃ and pressure of 100 torr, a growth thickness of 1μm and a Si doping concentration of 1×10⁻⁶ were achieved. 18 cm -3 The material is an N-type nitride layer of gallium nitride (denoted as n-type GaN layer).

[0138] (3) Growing an active layer on an n-type GaN layer, including the following steps:

[0139] S31: Adjust the temperature to 650℃ and the pressure to 100 torr to grow a quantum well layer (denoted as InGaN quantum well layer) with a thickness of 1nm on the n-type GaN layer.

[0140] S32: Raise the temperature to 700℃ to grow a 6nm thick GaN quantum barrier layer (denoted as GaN quantum barrier layer) on the InGaN quantum well layer to form a light-emitting unit.

[0141] S33: Repeat S31-S32 15 times to form an active layer with 15 light-emitting units.

[0142] (4) Growing a p-type nitride front layer on the active layer, including the following steps:

[0143] S41: Adjust the temperature to 700℃ and the pressure to 300 torr. First, introduce TMIn into the growth chamber at a flow rate of 50 sccm. The growth thickness is 3 nm, and the Mg doping concentration is 2 × 10⁻⁶. 19 cm -3 The Si doping concentration is 1×10⁻⁶. 17 cm -3 The first sub-layer.

[0144] S42: Adjust the TMIn flow rate to 500 sccm, grow a thickness of 2 nm, and set the Mg doping concentration to 2 × 10⁻⁶. 19 cm -3 The Si doping concentration is 1×10⁻⁶. 17 cm -3 The second sub-layer.

[0145] S43: Repeat S41-S42 twice to form a p-type nitride front layer (denoted as p-type GaN front layer) with a thickness of 10nm and made of gallium nitride.

[0146] (5) Depositing an atomic deposition layer containing Si and Mg (denoted as MgSi atomic deposition layer) on the p-type GaN front layer includes the following steps:

[0147] S51: Stop the flow of TMIn, linearly increase the temperature to 750℃ at a heating rate of 0.2℃ / s, adjust the pressure to 100 torr, and introduce Cp2Mg and SiH4 at a flow rate of 100 sccm to perform surface MgSi heat treatment on the p-type GaN front layer and maintain it for 5s to obtain a MgSi atomic deposition layer.

[0148] S52: Interrupt the introduction of Cp2Mg and SiH4, and continue heat treatment for 5 seconds to promote the full migration of Mg and Si atoms.

[0149] S53: Repeat S51-S52 three times alternately to form a MgSi atomic deposition layer with a thickness of 1 nm.

[0150] (6) The temperature was increased to 750℃ at a heating rate of 0.2℃ / s, and the pressure was adjusted to 200 torr. The growth thickness was 5nm and the Mg doping concentration was 2×10⁻⁶. 19 cm -3 The material is a p-type nitride back layer of GaN (denoted as p-type GaN back layer).

[0151] (7) Raise the temperature to 900℃ at a heating rate of 0.5℃ / s, adjust the pressure to 100 torr, and introduce NH3 with a flow rate of 20slm for N heat treatment;

[0152] During the N heat treatment, In in the p-type GaN front layer desorbs, and the MgSi atom deposition layer diffuses, with Mg atoms diffusing into the p-type GaN front layer and occupying the bonding vacancies formed by In desorption, thereby improving the Mg doping incorporation efficiency of the p-type GaN front layer; and Si atoms in the MgSi atom deposition layer diffuse into the p-type GaN back layer, transforming the single Mg-doped p-type GaN back layer into a Mg and Si co-doped p-type GaN back layer; after the MgSi atom deposition layer has completely diffused, the N heat treatment is stopped, forming a Mg and Si co-doped p-type GaN layer composed of the p-type GaN front layer and the p-type GaN back layer.

[0153] (8) Repeat steps (4) to (7) 6 times until a p-type nitride layer with a thickness of 90 nm and a material of GaN is formed (denoted as p-type GaN layer), thereby obtaining a nitride epitaxial wafer.

[0154] Example 3

[0155] This embodiment provides a method for preparing a nitride epitaxial wafer, which specifically includes the following steps:

[0156] (1) Place the sapphire substrate into the growth chamber of the organometallic chemical vapor deposition system.

[0157] (2) Under the conditions of temperature of 1250℃ and pressure of 300 torr, a growth thickness of 5μm and a Si doping concentration of 1×10⁻⁶ were achieved. 19 cm -3 The material is an N-type nitride layer of gallium nitride (denoted as n-type GaN layer).

[0158] (3) Growing an active layer on an n-type GaN layer, including the following steps:

[0159] S31: Adjust the temperature to 850℃ and the pressure to 400 torr to grow a quantum well layer (denoted as InGaN quantum well layer) with a thickness of 5nm on the n-type GaN layer.

[0160] S32: Raise the temperature to 950℃ to grow a 25nm thick GaN quantum barrier layer (denoted as GaN quantum barrier layer) on the InGaN quantum well layer to form a light-emitting unit;

[0161] S33: Repeat S31-S32 twice to form an active layer with two light-emitting units.

[0162] (4) Growing a p-type nitride front layer on the active layer, including the following steps:

[0163] S41: Adjust the temperature to 800℃ and the pressure to 600 torr. First, introduce TMIn into the growth chamber at a flow rate of 200 sccm. The growth thickness is 15 nm, and the Mg doping concentration is 2 × 10⁻⁶. 20 cm -3 The Si doping concentration is 5×10⁻⁶. 18 cm -3 The first sub-layer.

[0164] S42: Adjust the TMI flow rate to 1000 sccm, grow to a thickness of 5 nm, and set the Mg doping concentration to 2 × 10⁻⁶. 20 cm -3 The Si doping concentration is 5×10⁻⁶. 18 cm -3 The second sub-layer.

[0165] S43: Repeat S41-S42 four times to form a p-type nitride front layer (denoted as p-type GaN front layer) with a thickness of 80nm and made of gallium nitride.

[0166] (5) Depositing an atomic deposition layer containing Si and Mg (denoted as MgSi atomic deposition layer) on the p-type GaN front layer includes the following steps:

[0167] S51: Stop the flow of TMIn, linearly increase the temperature to 850℃ at a heating rate of 0.3℃ / s, adjust the pressure to 400 torr, introduce Cp2Mg at a flow rate of 2000 sccm and SiH4 at a flow rate of 500 sccm, perform surface MgSi heat treatment on the p-type GaN front layer and maintain it for 60s to obtain a MgSi atomic deposition layer.

[0168] S52: Interrupt the introduction of Cp2Mg and SiH4, and continue heat treatment for 30s to promote the full migration of Mg and Si atoms.

[0169] S53: Repeat S51-S52 14 times alternately to form a MgSi atomic deposition layer with a thickness of 5nm.

[0170] (6) The temperature was increased to 850℃ at a heating rate of 0.3℃ / s, and the pressure was adjusted to 600 torr. The growth thickness was 20nm and the Mg doping concentration was 2×10⁻⁶. 20 cm -3 The material is a p-type nitride back layer of GaN (denoted as p-type GaN back layer).

[0171] (7) Increase the temperature to 1000℃ at a heating rate of 0.8℃ / s, adjust the pressure to 300 torr, and introduce NH3 with a flow rate of 100 slm for N heat treatment.

[0172] During the N heat treatment, In in the p-type GaN front layer desorbs, and the MgSi atom deposition layer diffuses, with Mg atoms diffusing into the p-type GaN front layer and occupying the bonding vacancies formed by In desorption, thereby improving the Mg doping incorporation efficiency of the p-type GaN front layer; and Si atoms in the MgSi atom deposition layer diffuse into the p-type GaN back layer, transforming the single Mg-doped p-type GaN back layer into a Mg and Si co-doped p-type GaN back layer; until the MgSi atom deposition layer has completely diffused, the N heat treatment is stopped, forming a Mg and Si co-doped p-type GaN layer composed of the p-type GaN front layer and the p-type GaN back layer.

[0173] (8) Repeat steps (4) to (7) twice to form a p-type nitride layer (denoted as p-type GaN layer) with a thickness of 200 nm and a material of GaN, thereby obtaining a nitride epitaxial wafer.

[0174] Example 4

[0175] Example 4 is basically the same as Example 1, except that in step (4), when growing the p-type nitride prelayer, TMIn is introduced at a constant flow rate, specifically including:

[0176] The temperature was adjusted to 750°C, and TMIn was introduced at a constant flow rate of 150 sccm to grow a p-type GaN front layer with the same thickness as in Example 1, and the same Mg and Si doping concentrations and materials.

[0177] The rest is the same as in Example 1, and will not be described again here.

[0178] Example 5

[0179] Example 5 is basically the same as Example 1, except that in step (4), when growing the p-type nitride prelayer, TMIn is introduced at a constant flow rate, specifically including:

[0180] The temperature was adjusted to 750°C, and TMIn was introduced at a constant flow rate of 800 sccm to grow a p-type GaN front layer with the same thickness as in Example 1, and the same Mg and Si doping concentrations and materials.

[0181] The rest is the same as in Example 1, and will not be described again here.

[0182] Example 6

[0183] Example 6 is basically the same as Example 1, except for step (5). Step (5) of Example 6 specifically includes:

[0184] Stop the flow of TMIn, linearly increase the temperature to 800°C at a heating rate of 0.3°C / s, adjust the pressure to 250 torr, and introduce Cp2Mg at a flow rate of 1000 sccm and SiH4 at a flow rate of 300 sccm to perform surface MgSi heat treatment on the p-type GaN front layer until a MgSi atomic deposition layer with the same thickness as in Example 1 is obtained.

[0185] The rest is the same as in Example 1, and will not be described again here.

[0186] Example 7

[0187] Example 7 is basically the same as Example 1, except for steps (4) and (5). Steps (4) and (5) of Example 7 specifically include:

[0188] (4) Adjust the temperature to 750°C and introduce TMIn at a constant flow rate of 800 sccm to grow a p-type GaN front layer with the same thickness as in Example 1 and the same Mg and Si doping concentration and material.

[0189] (5) Stop the flow of TMIn, increase the temperature linearly to 800℃ at a heating rate of 0.3℃ / s, adjust the pressure to 250 torr, and introduce Cp2Mg at a flow rate of 1000 sccm and SiH4 at a flow rate of 300 sccm to perform surface MgSi heat treatment on the p-type GaN front layer until the same thickness of MgSi atomic deposition layer as in Example 1 is obtained.

[0190] The rest is the same as in Example 1, and will not be described again here.

[0191] Comparative Example 1

[0192] Comparative Example 1 provides a method for preparing a nitride epitaxial wafer. Steps (1) to (3) are performed in the same manner as in Example 1, except that the method for forming the p-type nitride layer is different. The specific growth method is as follows:

[0193] A p-type GaN layer with a thickness of 110 nm was grown by introducing TEG at a flow rate of 360 sccm, Cp2Mg at a flow rate of 720 sccm, NH3 at a flow rate of 53 slm, and SiH4 at a flow rate of 140 sccm under conditions of 850℃ and 200 torr.

[0194] The rest is the same as in Example 1.

[0195] Comparative Example 2

[0196] Comparative Example 2 provides a method for preparing a nitride epitaxial wafer, which differs from Example 1 only in step (6). Step (6) of Comparative Example 2 specifically includes:

[0197] The temperature was increased to 820℃ at a heating rate of 0.3℃ / s, and the pressure was adjusted to 400 torr. The growth thickness was 15nm, and the Mg doping concentration was 1×10⁻⁶. 20 cm -3 The Si doping concentration is 1×10 18 cm -3 The material is a p-type GaN back layer.

[0198] The rest is the same as in Example 1, and will not be described again here.

[0199] Comparative Example 3

[0200] The only difference between Comparative Example 3 and Example 1 is that in step (7) of Comparative Example 3, the N heat treatment temperature is 800°C.

[0201] The low nitrogen heat treatment temperature resulted in insufficient indium atom detachment, affecting the diffusion and occupancy of Mg atoms in the MgSi deposition layer. This prevented the effective doping of Mg atoms to increase hole concentration, impacting carrier expansion and injection capabilities, and consequently affecting brightness and voltage performance. Furthermore, insufficient indium atom detachment led to large lattice distortions in the p-type nitride layer, increasing stress defects and affecting leakage current and ESD performance.

[0202] Comparative Example 4

[0203] The only difference between Comparative Example 4 and Example 1 is that in step (7) of Comparative Example 4, the N heat treatment temperature is 1100°C.

[0204] It was found that the N heat treatment temperature was too high, which led to the desorption of In atoms in the active layer, damaged the crystal quality of the active layer, and thus affected the brightness, leakage current and ESD performance.

[0205] The blue nitride epitaxial wafers obtained through the above embodiments and comparative examples were used to test the wavelength uniformity (std / nm) and full width at half maximum (HW / nm) of the epitaxial wafers prepared in the above embodiments and comparative examples using photoluminescence (PL). Micro-LEDs were then fabricated using the same process and tested using an LED optoelectronic performance tester. The tests included luminous intensity (Lop / mW) and voltage (VF / V) under a 2mA current injection condition, luminous intensity decay (droop / %) under a 1000mA current injection condition, and electrostatic discharge yield (ESD%) and leakage current yield (IR%) under reverse breakdown voltages of 2000V and 7V. The test results are shown in Table 1.

[0206] Table 1. Relevant performance of Micro-LEDs fabricated using nitride epitaxial wafers in the Examples and Comparative Examples

[0207] Group WLD / nm VF / V Lop / mW / 2mA ESD / % IR / % droop / % Example 1 465.1 2.84 13.7 99.8 99.9 35.1 Example 2 465.4 2.85 13.5 99.9 99.9 35.4 Example 3 465.1 2.85 13.7 99.8 99.8 35.5 Example 4 465.2 2.87 12.9 98.7 99.2 39.2 Example 5 465.7 2.87 11.4 93.1 94.7 41.3 Example 6 465.4 2.89 12.1 94.5 95.2 40.2 Example 7 465.7 3.01 10.2 93.1 92.6 42.6 Comparative Example 1 465.2 3.13 9.6 93.1 94.6 47.2 Comparative Example 2 465.0 3.07 9.9 94.1 93.6 41.5 Comparative Example 3 464.9 2.98 10.1 95.1 94.6 40.6 Comparative Example 4 465.1 2.89 9.7 96.1 95.6 39.6

[0208] In summary, the nitride epitaxial wafer fabrication method provided by this invention forms a MgSi atom deposition layer between a p-type nitride front layer and a p-type nitride back layer, and promotes the diffusion of Mg and Si atoms in the MgSi atom deposition layer. Si atoms diffuse into the p-type nitride back layer to form a Mg and Si co-doped p-type nitride back layer. Mg atoms diffuse into the p-type nitride front layer, improving the effective doping and incorporation efficiency of Mg atoms in the p-type nitride front layer and increasing the hole concentration in the p-type nitride layer. This provides a high-concentration hole injection for the nitride epitaxial wafer, balancing the injection balance of electrons in the n-type nitride layer and holes in the p-type nitride layer, thereby improving the brightness of the nitride epitaxial wafer, reducing the operating voltage, and reducing the droop effect that occurs in the nitride epitaxial wafer as the injection current increases. The nitride epitaxial wafer formed based on the above method is suitable for high-current operating conditions and meets the application requirements of high-power epitaxial wafers.

[0209] All aspects, embodiments, features, and examples of this invention are to be regarded as illustrative in all respects and are not intended to limit the invention, the scope of which is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0210] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0211] Although the invention has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of the invention, and that elements of the embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of the invention to adapt particular situations or materials to the teachings of the invention. Therefore, this invention is not intended to be limited to the specific embodiments disclosed for carrying out the invention, but rather is intended to encompass all embodiments falling within the scope of the appended claims. Moreover, unless specifically stated otherwise, any use of the terms first, second, etc., does not indicate any order or importance, but is used to distinguish one element from another.

Claims

1. A method for preparing a nitride epitaxial wafer, characterized in that, include: S1. An N-type nitride layer and an active layer are sequentially prepared on the substrate; S2. Under the condition of introducing a surfactant, a p-type nitride front layer is grown on the active layer; wherein the surfactant contains an active element, the p-type nitride front layer contains the active element, a first dopant element, and a second dopant element, the active element, the first dopant element, and the second dopant element are all different, the first dopant element is Mg, and the second dopant element is selected from any one of Si, O, and C. S3. With the surfactant supply stopped, an atomic deposition layer is deposited on the p-type nitride front layer; wherein the atomic deposition layer comprises the first dopant element and the second dopant element, and step S3 specifically includes: S31. Stop the flow of the surfactant, and perform a second heat treatment for a first set time under the condition of the first doping element source and the second doping element source being introduced; S32. Stop the flow of the surfactant, the first dopant source and the second dopant source, and perform a third heat treatment for a second set time; S33. Repeat S31-S32 a second preset number of times to form the atomic deposition layer; S4. A p-type nitride back layer with the first doped element is grown on the atomic deposition layer; S5. Perform a first heat treatment on the structure obtained in step S4 to desorb the active element in the p-type nitride front layer and to allow the first dopant element and the second dopant element in the atomic deposition layer to migrate into the p-type nitride front layer and the p-type nitride back layer, respectively. S6. Repeat S2-S5 at least once to obtain a p-type nitride layer.

2. The preparation method according to claim 1, characterized in that, The p-type nitride front layer includes a first sublayer and a second sublayer sequentially stacked on the active layer. Step S2 specifically includes: S21. The surfactant is introduced at a first flow rate to grow the first sublayer; S22. The surfactant is introduced at a second flow rate to grow the second sublayer on the first sublayer; S23. Repeat S21-S22 for the first preset number of times; Wherein, the first flow rate is less than the second flow rate.

3. The preparation method according to claim 2, characterized in that: The ratio of the first flow rate to the second flow rate is 1:20 to 1:

5.

4. The preparation method according to claim 3, characterized in that, The first flow rate is 50-200 sccm, and the second flow rate is 500-1000 sccm.

5. The preparation method according to claim 2, characterized in that, The first preset number of times is 2 to 5 times.

6. The preparation method according to claim 2, characterized in that, The thickness of the first sublayer is 3-15 nm, and the Mg doping concentration of the first sublayer is 2 × 10⁻⁶. 19 -2×10 20 cm -3 The Si doping concentration of the first sublayer is 1×10⁻⁶. 17 -5×10 18 cm -3 .

7. The preparation method according to claim 2, characterized in that, The thickness of the second sublayer is 2-5 nm, and the Mg doping concentration of the second sublayer is 2 × 10⁻⁶. 19 -2×10 20 cm -3 The Si doping concentration of the second sublayer is 1×10⁻⁶. 17 -5×10 18 cm -3 .

8. The preparation method according to claim 1, characterized in that, The first set time is 5~60s.

9. The preparation method according to claim 1, characterized in that, The second set time is 5~30s.

10. The preparation method according to claim 1, characterized in that, The thickness of the atomic deposition layer is 1~5 nm.

11. The preparation method according to claim 1, characterized in that, The second preset number of times is 3 to 14 times.

12. The preparation method according to claim 1, characterized in that, The temperatures in steps S2, S3, S4, and S5 are set to T respectively. a T b T c T d , among which, T a <T b T b ≤T c T c <T d During the preparation process, T a Heat up to T b T b Heat up to T c T c Heat up to T d Linear heating is employed, with a heating rate of 0.2~1℃ / s.

13. The preparation method according to claim 1, characterized in that, The growth of the p-type nitride front layer includes: introducing an In surfactant at a temperature of 700-800℃ and a pressure of 300-600 torr to grow a thickness of 5-20 nm and a Mg doping concentration of 2×10⁻⁶. 19 -2×10 20 cm -3 The Si doping concentration is 1×10 17 -5×10 18 cm -3 The p-type nitride front layer.

14. The preparation method according to claim 1, characterized in that, The growth of the p-type nitride back layer includes: growing a thickness of 5-20 nm and a Mg doping concentration of 2×10⁻⁶ under conditions of 750-850℃ and 200-600 torr. 19 -2×10 20 cm -3 The p-type nitride back layer.

15. The preparation method according to claim 1, characterized in that, Step S5 includes: introducing a nitrogen source to perform the first heat treatment at a temperature of 900-1000℃ and a pressure of 100-300 torr.

16. The preparation method according to claim 1, characterized in that, Step S6 includes: repeating S2-S5 2-6 times.

17. The preparation method according to claim 1, characterized in that, The growth of the N-type nitride layer includes: growing a thickness of 1-5 μm and a Si doping concentration of 1×10⁻⁶ under conditions of temperature of 1050-1250℃ and pressure of 100-300 torr. 18 -1×10 19 cm -3 The N-type nitride layer.

18. The preparation method according to claim 1, characterized in that, The surfactant is an In surfactant, and the active element is In.

19. The preparation method according to claim 1, characterized in that, The thickness of the N-type nitride layer is 1-5 μm.

20. The preparation method according to claim 1, characterized in that, The active layer includes a plurality of light-emitting units arranged sequentially along a direction away from the N-type nitride layer, and the growth of the light-emitting units includes: Quantum well layers with a thickness of 1-5 nm are grown under conditions of temperature 650-850℃ and pressure 100-400 torr. A quantum barrier layer with a thickness of 6-25 nm is grown on the quantum well layer under conditions of temperature of 700-950℃ and pressure of 100-400 torr.

21. A nitride epitaxial wafer, characterized in that, It is prepared by the preparation method according to any one of claims 1-20.

22. A semiconductor device, characterized in that, Includes the nitride epitaxial wafer as described in claim 21.

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