Method for preparing p-type nitride epitaxial structure, epitaxial structure and semiconductor device

Abstract

The application discloses a preparation method of a P-type nitride epitaxial structure, an epitaxial structure and a semiconductor device, and comprises the following steps: providing a substrate; sequentially growing a U-shaped nitride layer, a lightly-doped P-type nitride layer and a highly-doped P-type nitride layer grown by a delta doping method on the substrate; and performing annealing in a cavity; wherein the highly-doped P-type nitride layer is periodically grown, and each period of growth comprises the following steps: introducing an N source and a group III metal source, and adding a surface activator to form a non-doped nitride layer; cutting off the group III metal source and the surface activator, and performing N source purging; and introducing a doping source, wherein the doping elements of the doping source include Mg and Cu, the Mg element is a main doping element, and the Cu element is an auxiliary doping element. The application improves the P-type nitride carrier concentration while having good crystal quality and epitaxial surface quality.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, specifically to a method for preparing a P-type nitride epitaxial structure, the epitaxial structure, and a semiconductor device. Background Technology

[0002] Growing high-quality p-type GaN has always been a challenge in the semiconductor technology field, especially growing carrier concentrations greater than 1E18cm⁻¹. -3 In traditional methods, increasing the Mg concentration to improve the carrier concentration of p-type GaN actually results in poor epitaxial surface quality and crystal quality, leading to Mg cones and haze. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing a p-type nitride epitaxial structure, an epitaxial structure, and a semiconductor device, which improves the carrier concentration while having better crystal quality and epitaxial surface quality.

[0004] To address the aforementioned technical problems, this invention provides a method for preparing a p-type nitride epitaxial structure, comprising the following steps:

[0005] Provide substrate;

[0006] A U-shaped nitride layer, a lightly doped P-type nitride layer, and a heavily doped P-type nitride layer grown by delta doping are sequentially grown on the substrate.

[0007] Annealing is performed inside the cavity;

[0008] The highly p-doped nitride layer grows periodically, and each growth cycle includes the following steps:

[0009] By introducing an N source and a group III metal source, and adding a surface activator, a non-nitride layer is formed;

[0010] Disconnect the group III metal source and surfactant, and purge the N source;

[0011] A doping source is introduced, wherein the doping elements of the doping source include Mg and Cu, with Mg being the main doping element and Cu being the auxiliary doping element.

[0012] As a further improvement of the present invention, the growth of the U-shaped nitride layer includes the steps of: sequentially growing an undoped nitride buffer layer and an undoped nitride bottom layer on the substrate, wherein the growth thickness of the undoped nitride buffer layer is less than the growth thickness of the undoped nitride bottom layer.

[0013] As a further improvement of the present invention, the growth pressure of the lightly doped P-type nitride layer is less than that of the highly doped P-type nitride layer, and its growth thickness is greater than that of the highly doped P-type nitride layer. The Mg doping concentration in the lightly doped P-type nitride layer is one-third of the Mg doping concentration in the highly doped P-type nitride layer.

[0014] As a further improvement of the present invention, the growth thickness of the undoped nitride buffer layer is 20-50 nm, the growth thickness of the undoped nitride bottom layer is 2-5 μm; the growth pressure of the lightly doped p-type nitride layer is 100-200 Torr, and its growth thickness is 2-5 μm; the growth thickness of the highly doped p-type nitride layer is 0.5-2 μm, the growth pressure is 400-600 Torr, the growth temperature is 1000-1100℃, and the growth cycle is 200-300 cycles.

[0015] As a further improvement of the present invention, the N-source purging time is less than the doping source introduction time, and the doping source introduction time is less than the group III metal source introduction time.

[0016] As a further improvement of the present invention, the molar amount of the added surfactant is less than the molar amount of the group III metal source introduced; and the doping concentration of Cu in the doped source is less than the doping concentration of Mg.

[0017] As a further improvement of the present invention, the surface activator is In, and the molar ratio of the group III metal source to the surface activator is 5%-30%; the time for introducing the group III metal source and adding the surface activator is 10-30 seconds, the N source purging time is 2-5 seconds, and the doping source introduction time is 5-10 seconds; the doping concentration of Mg in the doping source is 1E20cm⁻¹. -3 -3E20cm -3 Furthermore, the ratio of Cu to Mg incorporated is 1:500 to 1:1200.

[0018] As a further improvement of the present invention, the N source is NH3, the group III metal source is a TMGa source or a TEGa source, the surface activator is introduced TMIn, and the doping source includes a Mg source and a Cu source, wherein the Mg source is Cp2Mg and the Cu source is a DMZ source or a DEZ source.

[0019] A p-type nitride epitaxial structure is prepared using the p-type nitride preparation method described above, wherein the carrier concentration of the p-type nitride epitaxial structure is 1E18cm⁻¹. -3 -5E18cm -3 , (002) The half-width of the XRD rocking curve is less than 300 arcsec, and (102) The half-width of the XRD rocking curve is less than 400 arcsec.

[0020] A semiconductor device comprising a P-type nitride epitaxial structure as described above.

[0021] The beneficial effects of this invention are:

[0022] The growth of the highly doped p-type nitride layer in this invention employs high-pressure delta doping. High pressure facilitates the incorporation of Mg, and delta doping technology effectively suppresses the formation of p-type GaN dislocations, improves crystal quality, reduces defect density, decreases self-compensation effects, and increases carrier concentration.

[0023] The growth of undoped p-type nitride layers using surface activators still yields p-type GaN structures. This significantly reduces the GaN surface formation energy, improves the surface activity of group III metal elements at lower temperatures, and alleviates surface stress. This allows for subsequent increases in p-type GaN doping concentration while ensuring that the surface quality of p-type GaN remains unaffected and that it has good crystal quality.

[0024] In the growth of a highly doped p-type nitride layer, the group III metal source and surfactant are cleaved, and the N source is purged to desorb group III metal atoms, forming Ga vacancies (V0). Ga This process allows more Mg atoms to be incorporated into and incorporated into Ga vacancies, and it also suppresses dislocation climb in GaN epitaxial layers, thereby reducing the dislocation density of GaN and improving crystal quality.

[0025] By using Mg and Cu co-doping, the introduction of Cu can form Cu Ga The low acceptor energy level reduces the formation of Mg-H complexes and the influence of Mg element self-compensation effect on doping concentration, thereby increasing the carrier concentration of P-type nitrides. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the P-type nitride structure of the present invention;

[0027] Figure 2 This is a schematic diagram of a cycle of heavily doped P-type nitride layer growth process according to the present invention;

[0028] Figure 3 This is a surface image of the P-type nitride epitaxial layer OM prepared in Example 1 of the present invention;

[0029] Figure 4 This is a surface image of the P-type nitride epitaxial layer OM prepared in Comparative Example 4 of this invention;

[0030] The labels in the figure are as follows: 1. Substrate; 2. Undoped nitride buffer layer; 3. Undoped bottom layer; 4. Lightly doped p-type nitride layer; 5. Heavily doped p-type nitride layer. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0032] As described in the background section, Mg is a deeply dominant element in GaN, exhibiting high energy levels and low activation rates. Increasing the Mg concentration to raise the carrier concentration in p-type GaN can drastically affect the stress and interface states of the epitaxial layer, resulting in poor surface and crystal quality of the p-type GaN epitaxial layer, leading to Mg cones and hazy conditions. Furthermore, Mg's self-compensation generates deep energy levels (such as Mg...). Ga V N The hole concentration actually decreased at donor levels (such as donor levels).

[0033] To address the technical challenge of P-type nitride quality, the inventors, through long-term dedicated research, discovered that growing a lightly doped P-type nitride layer on the substrate surface through a U-type nitride layer, followed by the re-growth of a heavily doped P-type GaN with a periodic structure, can improve the carrier concentration of the P-type nitride material while maintaining the epitaxial surface quality and crystal quality.

[0034] For details, please refer to Figure 1 This invention provides a method for preparing a p-type nitride epitaxial structure, comprising the following steps:

[0035] Substrate 1 is provided;

[0036] A U-shaped nitride layer, a lightly doped P-type nitride layer 4, and a highly doped P-type nitride layer 5 grown by delta doping are sequentially grown on substrate 1.

[0037] Annealing in an N2 atmosphere inside the cavity;

[0038] Among them, the highly p-doped nitride layer 5 grows periodically, and each growth cycle includes the following steps:

[0039] By introducing an N source and a group III metal source, and adding a surface activator, a non-nitride layer is formed; the surface activator is In.

[0040] Disconnect the group III metal source and surfactant, and purge the N source to desorb the group III metal atoms;

[0041] A doping source is introduced, and the doping elements in the doping source include Mg and Cu, with Mg being the main doping element and Cu being the auxiliary doping element.

[0042] This invention uses p-type GaN epitaxial structures as an example to explain its key principles and processes: Increasing the Mg concentration to improve the carrier concentration of p-type GaN actually worsens the surface and crystal quality of the p-type GaN epitaxial structure, and reduces the hole concentration. Therefore, this invention improves delta doping technology to increase the carrier concentration of p-type nitride materials while maintaining the surface and crystal quality of GaN.

[0043] Specifically, this invention first grows a U-shaped GaN layer on substrate 1, which includes an undoped nitride buffer layer 2 and an undoped nitride bottom layer 3 grown sequentially on substrate 1. The function of the entire U-shaped GaN layer is to transition the heterogeneous substrate to a flat GaN material layer. It needs a certain thickness. Therefore, it first grows 20-50nm as a buffer, and then gradually transitions to flatness, growing 2-5μm. It has a certain thickness to meet the requirements of the transition flatness. The undoped nitride buffer layer 2 is small and grows slowly, serving as a GaN buffer. The undoped nitride bottom layer 3 is thicker and grows faster than the undoped nitride buffer layer 2, providing a better surface for the growth of p-type GaN. In addition, the undoped GaN has a higher background concentration, which can form a PN junction with the p-layer, which is beneficial for subsequent Hall tests.

[0044] After the U-type GaN material is grown, a lightly doped P-type GaN layer is extended to prepare for subsequent growth. This 2-5 μm thick layer is grown under a pressure of 100-200 Torr (because light Mg doping does not require excessively high pressure, it needs to be lower than the pressure used in heavy doping), at a temperature of 1000-1200℃. This layer serves two purposes: First, it eliminates the influence of the depletion layer. Although the underlying material is U-type GaN, due to the properties of GaN, it still exhibits weak N-type characteristics. To avoid affecting the subsequent P-type layer, this layer is lightly doped with Mg to neutralize the depletion layer. The doping concentration is referenced to the thickness and background concentration of the U-type layer. Second, it provides stress relief and interface states for the subsequent highly doped P-type layer. High doping can drastically affect the stress and interface states of the epitaxial layer, while the lightly doped P-type GaN layer acts as a transition, promoting the Mg incorporation rate and good surface morphology of the highly doped P-type layer. In this invention, the Mg doping concentration in the lightly doped P-type GaN layer is one-third that in the heavily doped P-type GaN layer, and it is greater than the thickness of the heavily doped P-type GaN layer. As part of the P-type epitaxial layer, the lightly doped P-type nitride layer occupies a relatively large thickness in the entire epitaxial structure, which is beneficial for neutralizing the weak N-type of U-type GaN and acts as a transition layer for the subsequent heavily doped P-type GaN layer, facilitating the incorporation of more Mg into the subsequent heavily doped P-type GaN.

[0045] When constructing heavily doped p-type GaN layers, a high-pressure delta doping method is used to grow layers approximately 0.5-2 μm thick. The growth pressure is 400-600 Torr (high pressure), and the growth temperature is 1000-1100℃. The growth cycle is 200-300 cycles. The higher growth temperature facilitates the incorporation of Mg and Cu, resulting in a smoother surface. The high pressure promotes Mg incorporation. Delta doping effectively suppresses the formation of p-type GaN dislocations, improves crystal quality, reduces defect density, minimizes self-compensation effects, and increases carrier concentration. The specific principles and processes are as follows: Figure 2 As shown, in one cycle:

[0046] 1) NH3 is always introduced, and TMGa and TMIn sources are introduced first to grow an undoped p-type nitride layer for 10-30 seconds. In is used as a surface activator. The molar ratio of TMGa and TMIn sources is 5%-30%. The obtained structure is still p-type GaN. This can significantly reduce the surface formation energy of GaN, improve the surface activity of group III metal elements at lower temperatures, and reduce surface stress. This ensures that the surface quality of p-type GaN is not affected while increasing the doping concentration of p-type GaN, and also has good crystal quality.

[0047] 2) Turn off the TMGa source and TMIn source, and purge with NH3 for 2-5 seconds to desorb the group III metal atoms (this desorption process does not include the desorption of the surface activator, because the molar amount of the activator is much smaller than the amount incorporated by the TMGa source, and it only acts as a surface activator. Therefore, the grown structure is still p-type GaN, so this step is only for the desorption of Ga), forming Ga vacancies (VGa) so that more Mg atoms can be incorporated and incorporated into the Ga vacancies. This process also inhibits the climbing of dislocations in GaN epilayer, thereby reducing the dislocation density of GaN.

[0048] 3) Maintain the NH3 flow rate and introduce the Cp2Mg source and DMZ source for 5-10 seconds, with a Mg doping concentration of 1E20cm⁻¹. -3 -3E20cm -3 Furthermore, the ratio of Cu to Mg incorporated is 1:500-1:1200, employing a dual-element co-doping method with Mg and Cu. Introducing Cu allows the formation of Cu... Ga The acceptor level is low (the 3d electrons of Cu and the 2p electrons of N work together to split and form several shallower acceptor levels), and the formation of Cu-N complexes reduces V. NThe compensation effect generated by the donor reduces the formation of Mg-H complexes and the influence of Mg element self-compensation effect on the doping concentration, thereby increasing the carrier concentration of P-type nitrides. However, Cu has a large atomic radius, so the doping concentration cannot be too high, as it introduces more dislocations and reduces mobility. Therefore, while using Mg / Cu co-doping to increase the carrier concentration, controlling Cu within a certain range can obtain a better epitaxial surface without Mg cones and haze. In this embodiment, the N-source purging time (2-5 seconds) is shorter than the dopant source introduction time (5-10 seconds), and the dopant source introduction time is shorter than the group III metal source introduction time. This ensures the formation of the doped group III metal nitride layer while also ensuring the desorption of group III metal atoms during the N-source purging process. However, the N-source purging time cannot be too long, as this would extend the process time and increase the amount of desorption, resulting in too many Ga vacancies, which is not conducive to the formation of high-quality crystals. At the same time, the molar amount of surface activator added is less than the molar amount of the group III metal source introduced, so that the amount of activator can be controlled to achieve the surface activation effect. When there is too much In dopant, In particles will form on the surface. Since In has a low melting point, it will form In droplet structures and alloy-like substances, affecting the semiconductor properties of the layer structure. The doping concentration of Cu, as an auxiliary dopant source, is less than the doping concentration of Mg, the main dopant source.

[0049] Annealing in an N2 atmosphere inside the cavity aims to reduce Mg-H complexes and improve the activation efficiency of Mg.

[0050] Furthermore, the group III metal source can be a TMGa source or a TEGa source, and the Cu source can be a DMZ source or a DEZ source.

[0051] This invention also provides a p-type nitride epitaxial structure, prepared using the p-type nitride preparation method described above, wherein the carrier concentration of the p-type nitride epitaxial structure is 1E18cm⁻¹. -3 -5E18cm -3 The half-width at half maximum (WHM) of the (002) XRD rocking curve is less than 300 arcsec, and the half-width at half maximum (WHM) of the (102) XRD rocking curve is less than 400 arcsec. Among them, the wider the WHM of the X-ray diffraction rocking curve, the worse the crystal quality, and conversely, the narrower the WHM, the better the crystal quality.

[0052] The effects and properties of the above method and the obtained P-type nitride epitaxial structure will be illustrated below through examples and comparative examples.

[0053] Example 1

[0054] This embodiment describes the fabrication and testing of a p-type GaN structure, specifically including the following steps:

[0055] (1) Using sapphire as a substrate;

[0056] (2) After growing an undoped GaN buffer layer of about 50 nm, grow an undoped GaN layer of about 2 μm as the bottom layer;

[0057] (3) Grow a low-doped p-type GaN layer of about 2 μm at a growth pressure of 150 Torr and a growth temperature of 1090℃;

[0058] (4) A highly doped p-type GaN layer of about 550 nm was grown using delta doping. The growth pressure was 500 Torr and the growth temperature was 1045 °C. The following steps constitute one cycle of growth, and a total of 300 cycles were performed:

[0059] (41) Keep NH3 flowing in and introduce TMGa and TMIn sources for 15 seconds. The flow rate of TMGa is 40 sccm and the TMIn:TMGa ratio is 10%.

[0060] (42) Then turn off the TMGa source and TMIn source, and purge with NH3 for 4 seconds to cause desorption of group III metal atoms;

[0061] (43) Then maintain the NH3 flow rate and pass through the Cp2Mg source and DMZ source for 5 seconds. The Mg doping concentration is 2000 sccm and the Cu:Mg = 1:1000.

[0062] (5) Annealing in an N2 atmosphere inside the cavity.

[0063] Comparative Example 1

[0064] The difference between Comparative Example 1 and Example 1 is that no TMIn source is introduced in step (41), that is, no surfactant is added, but otherwise it is the same as Example 1.

[0065] Comparative Example 2

[0066] The difference between Comparative Example 2 and Example 1 is that the NH3 purging in step (42) is not performed, that is, step (42) is deleted and step (43) is performed directly. Otherwise, it is the same as Example 1.

[0067] Comparative Example 3

[0068] The difference between Comparative Example 3 and Example 1 is that in step (43), only the Cp2Mg source is introduced and the DMZ source is not introduced, that is, the growth is not Cu-doped, and the rest is the same as Example 1.

[0069] Comparative Example 4

[0070] The difference between Comparative Example 3 and Example 1 is that: in step (4), the improved delta doping method is not used to grow a highly p-doped GaN layer. Instead, a highly p-doped GaN layer of about 550 nm is grown directly after step (3). The doping concentration of Mg is Cp2Mg and the flow rate is 2000 sccm. The rest is the same as in Example 1.

[0071] The P-type GaN structure samples prepared in Example 1 and Comparative Examples 1-4 were subjected to the following tests: 1) Hall effect testing under a Hall current of 0.0049 mA; 2) XRD testing; and 3) OM surface visualization. The results of the obtained P-type layers are shown in Table 1 and... Figure 3 and Figure 4 As shown:

[0072] Table 1:

[0073]

[0074] As can be seen from Table 1: 1. Compared with Example 1, the carrier concentration of the heavily doped P-type layer prepared in Comparative Example 1 decreased, the half-maximum width increased, and the crystal quality decreased. The reason is that the GaN surface formation energy is high, the surface activity of the group III metal elements is insufficient at lower temperatures, and the stress is large, which affects the subsequent high Mg doping incorporation rate, resulting in a decrease in the carrier concentration of the final P-type layer and affecting the crystal quality. This further illustrates the role of In as an activator in Example 1, which significantly reduces the GaN surface formation energy, improves the surface activity of the group III metal elements at lower temperatures, and improves the Mg incorporation rate and crystal quality.

[0075] 2. Compared with Example 1, Comparative Example 2 showed a decrease in P-type layer carrier concentration, a wider half-width, and a decrease in crystal quality. Due to the adsorption of group III metal atoms, there were no more Ga vacancies for Mg atoms to incorporate, resulting in a decrease in Mg incorporation rate and a decrease in P-type layer carrier concentration. Furthermore, dislocation climbing occurred in the GaN epitaxial layer, reducing crystal quality. This further demonstrates that NH3 purging in Example 1 can desorb group III metal atoms, forming Ga vacancies (VGa) so that more Mg atoms can be incorporated and incorporated into the Ga vacancies. It can also suppress dislocation climbing in the GaN epitaxial layer, thereby reducing the dislocation density of GaN and improving crystal quality.

[0076] 3. The carrier concentration of the P-type layer prepared in Comparative Example 3 was significantly lower than that in Example 1, while the full width at half maximum (FWHM) did not change significantly, and the crystal quality was the same as in Example 1. This is because although an activator was added to the delta doping in Comparative Example 3, increasing the GaN surface formation energy (i.e., increasing the Mg incorporation rate to some extent), it could not further suppress the self-compensation effect of Mg, thus failing to generate deep energy levels (such as Mg). Ga V NThe concentration of holes in donor levels (such as Cu) actually decreased; this further illustrates the role of Cu doping in Example 1, forming Cu Ga The lower acceptor energy level increases the activation rate, and the formation of Cu-N complexes reduces V. N The compensation effect generated by the donor reduces the formation of Mg-H complexes and the influence of the self-compensation effect of Mg on the doping concentration, thereby increasing the carrier concentration.

[0077] 4. The method in Comparative Example 4 is a traditional highly p-doped GaN, whose OM surface is as follows: Figure 4 As shown, the formation of Mg cones and haze is illustrated, while the surface morphology of the epitaxial wafer obtained in Example 1 is shown in the figure. Figure 3 As shown, the surface is smooth, without haze or a large number of Mg cone morphologies. Through the verification of Comparative Examples 1-3, it is further proved that In as an activator, the NH3 purging process, and the co-doping of Cu / Mg in Example 1 have the effect of improving carrier concentration and crystal quality, while ensuring the quality of the epitaxial wafer surface morphology.

[0078] Example 2

[0079] To further illustrate the effect of high pressure on heavily p-doped GaN layers, this embodiment changes the growth pressure of the heavily p-doped GaN layer compared to Embodiment 1, while the rest is the same as Embodiment 1;

[0080] 1) The growth pressure in step 4) of Example 1 is 400 Torr;

[0081] 2) The growth pressure in step 4) of Example 1 is 600 Torr;

[0082] The P-type GaN structure samples prepared under the two growth pressures in Examples 1 and 2 were subjected to Hall effect testing and XRD analysis under a Hall current of 0.0049 mA. The results of the P-type layer analysis are shown in Table 2.

[0083] Table 2:

[0084]

[0085] The results show that as the growth pressure increases, the carrier concentration increases (500 Torr in Example 1 is higher than that in Example 2 (1)), that is, the Mg doping rate increases, and high pressure is beneficial to Mg doping; and as the pressure increases, the half-width decreases, and the crystal quality also improves; however, the growth pressure should not be too high, as it will cause decomposition side reactions and make it impossible to grow a flat epitaxial layer.

[0086] Example 3

[0087] For growing highly p-doped GaN layers, the NH3 purging and Mg passing times must be strictly controlled in each cycle to prevent GaN from decomposing under high pressure. This embodiment changes the NH3 purging and Mg passing times compared to Example 1, but the rest is the same as Example 1.

[0088] 1) The NH3 purging time in step (42) of Example 1 is 2 seconds;

[0089] 2) The NH3 purging time in step (42) of Example 1 is 5 seconds;

[0090] The P-type GaN structure samples prepared under the two purge times in Examples 1 and 3 were subjected to Hall effect testing and XRD analysis under a Hall current of 0.0049 mA. The results of the P-type layer analysis are shown in Table 3.

[0091] Table 3:

[0092]

[0093] The results show that under high pressure conditions, the purging time for each cycle should not be too short or too long.

[0094] Too short: Group III metal atoms do not have enough time to desorb, there are not enough Ga vacancies for Mg atoms to incorporate, the Mg incorporation rate decreases, the carrier concentration of the P-type layer decreases, and the suppression of dislocation climb time in the epitaxial layer is short, resulting in reduced crystal quality (the half-width at half maximum is wider than in Example 1).

[0095] Excessive growth time can lead to decomposition side reactions, significantly reducing the growth rate, decreasing carrier concentration, and affecting crystal quality.

[0096] The present invention also provides a semiconductor device comprising a P-type nitride epitaxial structure as described in any of the above embodiments or examples.

[0097] The above-described embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention. The scope of protection of the present invention is defined by the claims.

Claims

1. A method for preparing a p-type nitride epitaxial structure, characterized in that: Includes the following steps: Provide substrate; A U-type nitride layer, a lightly doped P-type nitride layer, and a highly doped P-type nitride layer grown by delta doping are sequentially grown on the substrate. Annealing is performed inside the cavity; The highly p-doped nitride layer grows periodically, and each growth cycle includes the following steps: By introducing an N source and a group III metal source, and adding a surface activator, a non-nitride layer is formed; Disconnect the group III metal source and surfactant, and purge the N source; A doping source is introduced, wherein the doping elements of the doping source include Mg and Cu, with Mg being the main doping element and Cu being the auxiliary doping element; The growth pressure of the lightly doped P-type nitride layer is lower than that of the heavily doped P-type nitride layer, and the doping concentration of Cu in the doping source is lower than that of Mg.

2. The method for preparing the p-type nitride epitaxial structure as described in claim 1, characterized in that: The growth of the U-shaped nitride layer includes the steps of sequentially growing an undoped nitride buffer layer and an undoped nitride bottom layer on the substrate, wherein the growth thickness of the undoped nitride buffer layer is less than the growth thickness of the undoped nitride bottom layer.

3. The method for preparing the p-type nitride epitaxial structure as described in claim 1, characterized in that: The growth thickness of the lightly doped P-type nitride layer is greater than that of the highly doped P-type nitride layer, and the Mg doping concentration in the lightly doped P-type nitride layer is one-third of the Mg doping concentration in the highly doped P-type nitride layer.

4. The method for preparing the p-type nitride epitaxial structure as described in claim 2, characterized in that: The growth thickness of the undoped nitride buffer layer is 20-50 nm, and the growth thickness of the undoped nitride substrate is 2-5 μm; the growth pressure of the lightly doped p-type nitride layer is 100-200 Torr, and its growth thickness is 2-5 μm; the growth thickness of the heavily doped p-type nitride layer is 0.5-2 μm, the growth pressure is 400-600 Torr, the growth temperature is 1000-1100℃, and the growth cycle is 200-300 cycles.

5. The method for preparing a p-type nitride epitaxial structure as described in claim 1, characterized in that: The purge time of the N-source is less than the time for introducing the doped source, and the time for introducing the doped source is less than the time for introducing the group III metal source.

6. The method for preparing a p-type nitride epitaxial structure as described in claim 1, characterized in that: The molar amount of surfactant added is less than the molar amount of the group III metal source introduced.

7. The method for preparing the p-type nitride epitaxial structure as described in claim 5 or 6, characterized in that: The surface activator is In, and the molar ratio of the group III metal source to the surface activator is 5%-30%; the time for introducing the group III metal source and adding the surface activator is 10-30 seconds, the N source purging time is 2-5 seconds, and the doping source introduction time is 5-10 seconds; the doping concentration of Mg in the doping source is 1E20cm⁻¹. -3 -3E20cm -3 Furthermore, the ratio of Cu to Mg incorporated is 1:500 to 1:1200.

8. The method for preparing a p-type nitride epitaxial structure as described in claim 1, characterized in that: The N source is NH3, the group III metal source is a TMGa source or a TEGa source, the surface activator is introduced TMIn, and the doping source includes a Mg source and a Cu source, wherein the Mg source is Cp2Mg and the Cu source is a DMZ source or a DEZ source.

9. A p-type nitride epitaxial structure, characterized in that: The p-type nitride epitaxial structure is prepared using the method described in any one of claims 1-8, wherein the carrier concentration of the p-type nitride epitaxial structure is 1E18cm⁻¹. -3 -5E18cm -3 , (002) The half-width of the XRD rocking curve is less than 300 arcsec, and (102) The half-width of the XRD rocking curve is less than 400 arcsec.

10. A semiconductor device, characterized in that: Including a p-type nitride epitaxial structure as described in claim 9.

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