A method for preparing an epitaxial structure of a photoelectric device, an epitaxial structure and a photoelectric device

Abstract

The application discloses a preparation method of an epitaxial structure of a photoelectric device, an epitaxial structure and a photoelectric device. The preparation method comprises the following steps: S1, cleaning and etching a surface of an N-type single crystal substrate to form a first structure layer under first process parameters; S2, three-dimensional growth is performed on the first structure layer under second process parameters to form a second structure layer with a roughness of 1-10 nm; S3, a quantum well active layer is grown on the second structure layer, and an upper surface of the quantum well active layer forms a third structure layer; and S4, a P-type semiconductor layer is grown on the quantum well active layer, and the surface of the P-type semiconductor layer is flat. The preparation method provided in the application can release the stress of the quantum well active layer without sacrificing the crystal quality, increase the injection efficiency of In components, increase the light emitting area of the quantum well, improve the light emitting efficiency, and the prepared epitaxial structure is thinner, and is suitable for the preparation of an ultrathin photoelectric device.

Description

Technical Field

[0001] This invention specifically relates to a method for preparing an epitaxial structure for an optoelectronic device, the epitaxial structure, and the optoelectronic device, belonging to the field of semiconductor manufacturing technology. Background Technology

[0002] Group III nitride semiconductors are known as third-generation semiconductor materials. They have advantages such as a large bandgap, good chemical stability, and strong radiation resistance. Their bandgap covers the range from deep ultraviolet, the entire visible light spectrum, to the near-infrared spectrum, and they are widely used in optoelectronic devices.

[0003] Currently, optoelectronic devices based on gallium nitride (GaN) materials typically employ heteroepitaxial structures, where GaN materials are grown on heteroepitaxial substrates, such as sapphire or silicon substrates. Heteroepitaxial GaN materials exhibit a high dislocation density; despite numerous methods proposed to reduce dislocations, the density remains as high as 10⁸ cm⁻¹. -2 To improve epitaxial quality, a thicker underlying layer is necessary. However, increasing the underlying layer thickness not only increases costs but also degrades the performance of some devices, such as Micro-LEDs. Due to their small chip size, sidewall damage during dicing significantly impacts chip performance, and the extent of sidewall damage is directly related to the epitaxial layer thickness. Therefore, thickness limitations restrict device performance to some extent.

[0004] Furthermore, GaN-based optoelectronic devices require the growth of quantum well structures using InGaN material as the light-emitting trap. In existing technologies, as shown in Figure 1, a complex preparatory layer is needed to create V-shaped pits before growing the quantum well structure to increase the light-emitting area and thus enhance luminous efficiency. However, creating the V-shaped pits requires forming a preparatory layer, which also increases the device thickness and growth time cost. Summary of the Invention

[0005] The main objective of this invention is to provide an epitaxial structure for optoelectronic devices based on GaN homoepitaxial growth, its fabrication method, and its application, so as to overcome the shortcomings of the prior art.

[0006] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0007] One aspect of the present invention provides a method for fabricating an epitaxial structure of an optoelectronic device, comprising:

[0008] S1. Under the first process parameters, the surface of the N-type single crystal substrate is cleaned and etched to form the first structural layer;

[0009] S2. Under the second process parameters, the first structural layer is grown in three dimensions to form a second structural layer with a roughness of 1-10 nm.

[0010] Wherein, the first process parameter includes at least a first temperature, and the second process parameter includes at least a second temperature; the second temperature is lower than the first temperature; and the roughness of the second structural layer is greater than the roughness of the first structural layer.

[0011] S3. A quantum well active layer is grown on the second structural layer, and a third structural layer is formed on the upper surface of the quantum well active layer; wherein the roughness of the third structural layer is not greater than the roughness of the second structural layer.

[0012] S4. Grow a P-type semiconductor layer on the active layer of the quantum well and make the surface of the P-type semiconductor layer flat.

[0013] Furthermore, step S1 includes:

[0014] The surface of an N-type single crystal substrate is cleaned in a hydrogen and NH3 atmosphere, and in-situ etching of the surface is performed by utilizing the breaking of NH3 to form a first structural layer with unevenness on the surface of the single crystal substrate.

[0015] Furthermore, step S1 specifically includes:

[0016] Under a hydrogen atmosphere, the temperature is adjusted to the first temperature, and NH3 is turned on for at least 5 minutes to clean the surface of the N-type single crystal substrate; then, NH3 is alternately turned on and off for 10-30 seconds to perform in-situ etching on the surface of the N-type single crystal substrate; wherein, the first temperature is 1050-1100℃.

[0017] Furthermore, the first process parameter includes at least a first pressure, and the second process parameter includes at least a second pressure; the first pressure is less than the second pressure; and the second pressure is 400-500 torr.

[0018] Furthermore, the second process parameter also includes the V / III value.

[0019] Furthermore, step S2 specifically includes:

[0020] At a second temperature, the V / III value is controlled to be 500-1000 to perform three-dimensional growth on the first structural layer, wherein the three-dimensional growth time is 5-10 min and the second temperature is 900-950℃.

[0021] Furthermore, step S2 specifically includes:

[0022] During three-dimensional growth, N-type doping is introduced, including TMIn source and SiH4.

[0023] Furthermore, steps S1 to S4 are performed continuously within the same reaction chamber.

[0024] Another aspect of the present invention provides an epitaxial structure for an optoelectronic device, comprising:

[0025] N-type single crystal substrate; a first structural layer and a second structural layer are formed on the surface of the N-type single crystal substrate, the roughness of the second structural layer is greater than that of the first structural layer; the second structural layer includes a plurality of opposing protrusions and / or a plurality of opposing recesses.

[0026] A quantum well active layer; the quantum well active layer is formed on the second structural layer, and a third structural layer is formed on the upper surface of the quantum well active layer, the roughness of the third structural layer being equal to or slightly less than the roughness of the second structural layer; the third structural layer includes a plurality of opposing protrusions and / or a plurality of opposing recesses;

[0027] A P-type semiconductor layer is formed on the active layer of the quantum well, and the surface of the P-type semiconductor layer is flat.

[0028] Furthermore, the roughness of the second structural layer is 1-10 nm.

[0029] Furthermore, the total thickness of the first structural layer and the second structural layer is 100-300 nm.

[0030] Furthermore, the thickness of the epitaxial structure is 1-2 μm.

[0031] Furthermore, the N-type single crystal substrate includes an N-type GaN single crystal substrate.

[0032] Another aspect of the present invention provides an optoelectronic device fabricated using the above-described epitaxial structure.

[0033] Compared with the prior art, the advantages of the present invention include:

[0034] 1) A method for fabricating an epitaxial structure for optoelectronic devices is provided. Using an N-type GaN single crystal substrate, the epitaxial structure formed by growth eliminates the need for a thicker underlying layer compared to traditional heteroepitaxial structures, resulting in a thinner structure that is more suitable for ultra-thin optoelectronic devices (such as Micro-LEDs) and saves costs.

[0035] 2) A method for fabricating an epitaxial structure for an optoelectronic device is provided. First, impurities such as O and C on the surface of an N-type GaN single crystal substrate are removed by in-situ etching, and a first structural layer with uneven surfaces is formed on the surface of the N-type GaN single crystal substrate. Then, the first structural layer is three-dimensionally grown by controlling the process parameters to form a second structural layer with a roughness of 1-10 nm. A subsequent quantum well active layer is then epitaxially grown on this second structural layer, so that the growth mode of the quantum well active layer continues that of the second structural layer, thereby forming a quantum well active layer with a third structural layer on the surface. This method can release the stress of the quantum well active layer without sacrificing crystal quality, thereby improving the injection efficiency of In in the InGaN quantum well active layer and increasing the light-emitting area of ​​the quantum well, which can effectively improve the optoelectronic performance of the optoelectronic device.

[0036] 3) A method for fabricating an epitaxial structure of an optoelectronic device is provided, which eliminates the need for growing a preparation layer used to create V-shaped pits in traditional epitaxial structures, and further reduces the thickness of the epitaxial structure. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0038] Figure 1 This is a schematic diagram of a three-dimensional quantum well structure obtained by amplifying dislocations to form V-shaped pits in existing heteroepitaxial structures;

[0039] Figure 2 This is a schematic diagram of an epitaxial structure of an optoelectronic device based on GaN homoepitaxial growth, provided in a typical embodiment of the present invention.

[0040] Figures 3a to 3d This is a schematic diagram of the fabrication process of an epitaxial structure for an optoelectronic device based on GaN homoepitaxial growth, provided in a typical embodiment of the present invention.

[0041] Figure 4 This is a surface morphology diagram of an N-type GaN single crystal substrate after three-dimensional growth roughening treatment in a typical embodiment of the present invention.

[0042] Figure 5 This is a schematic diagram comparing the Raman spectra of an N-type GaN single crystal substrate before and after three-dimensional growth roughening treatment in a typical embodiment of the present invention.

[0043] Figure 6This is a schematic diagram illustrating the relationship between the emission wavelength of an epitaxial structure of a GaN homoepitaxial optoelectronic device and the surface roughness of an N-type GaN single crystal substrate, provided in a typical embodiment of the present invention. Detailed Implementation

[0044] In view of the shortcomings of existing technologies, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The invention provides a method for fabricating epitaxial structures of optoelectronic devices, which forms a V-shaped quantum well structure through in-situ etching and three-dimensional roughening, rather than by amplifying dislocations or sacrificing crystal quality. Furthermore, by changing the process conditions, the size and density of the roughened structure pattern can be precisely and quantitatively controlled, allowing for subsequent optimization design of the target optoelectronic device's performance, thus demonstrating strong operability.

[0045] Please see Figure 2 A typical embodiment of the present invention provides an epitaxial structure for an optoelectronic device comprising, from bottom to top, an N-type GaN single crystal substrate 10, an InGaN quantum well active layer 20, and a P-type GaN layer 30.

[0046] The N-type GaN single crystal substrate 10 has a first structural layer and a second structural layer on its surface. The roughness of the second structural layer is greater than that of the first structural layer. It should be noted that the second structural layer is formed by three-dimensional roughening growth of the first structural layer. Figure 2 The second structural layer is integrated with the first structural layer. The first structural layer will be explained in detail in the subsequent epitaxial structure fabrication process.

[0047] Specifically, the roughness of the second structural layer is 1-10 nm, and it includes a plurality of opposing protrusions 101 and a plurality of opposing recesses 102.

[0048] Specifically, the total thickness of the first and second structural layers is 100-300 nm.

[0049] Specifically, the InGaN quantum well active layer 20 is grown on the second structural layer and continues the growth pattern of the second structural layer. Then, a third structural layer is formed on the surface of the InGaN quantum well active layer 20. The roughness of the third structural layer is not greater than the roughness of the second structural layer. The roughness includes equal to or slightly less than. More preferably, the roughness of the third structural layer is equal to the roughness of the second structural layer. That is, the third structural layer has an uneven morphology consistent with the second structural layer, which includes multiple relative protrusions 201 and multiple relative depressions 202. The P-type GaN layer 30 is grown on the second roughened structure. The surface of the InGaN quantum well active layer 20 is filled by the P-type GaN layer 30, and the P-type GaN layer 30 finally has a flat surface.

[0050] Furthermore, a method for preparing the GaN-based homoepitaxial optoelectronic device epitaxial structure provided in this typical embodiment includes:

[0051] S1, providing such Figure 3a The N-type GaN single crystal substrate 10 shown is subjected to cleaning and in-situ etching on its surface under first process parameters to form a first structural layer comprising multiple protrusion structures 103 on the surface of the N-type GaN single crystal substrate 10, such as... Figure 3b As shown. This process can both clean impurities such as O and C from the surface of the N-type GaN single crystal substrate 10 and etch its surface. The first process parameters include at least a first temperature and a first pressure. Preferably, the first temperature is 1050-1100℃ and the first pressure is 200-300 torr.

[0052] S2. Under the second process parameters, controlling the V / III value to be 500-1000, perform three-dimensional growth on the first structural layer on the surface of the N-type GaN single crystal substrate 10 for 5-10 minutes to form a second structural layer with a roughness of 1-10 nm. The roughness of the second structural layer is greater than that of the first structural layer. The second structural layer includes multiple relatively protruding portions 101 and multiple relatively recessed portions 102, such as... Figure 3c As shown. The second process parameters include at least a second temperature and a second pressure, wherein the second temperature is lower than the first temperature and the second pressure is higher than the first pressure. Preferably, the second temperature is 900-950℃ and the second pressure is 400-500 torr.

[0053] In this step, a second structural layer with a roughness of 1-10 nm is formed by three-dimensional roughening of the first structural layer on the surface of the N-type GaN single crystal substrate 10. This effectively increases the tensile stress, which is beneficial for the implantation of In components into the subsequently grown InGaN quantum well active layer 20. Furthermore, when the surface roughness is in the range of 1-10 nm, the greater the roughness, the higher the In implantation efficiency in the InGaN quantum well active layer 20. It should be noted that the surface roughness Ra of the second structural layer is preferably 1-10 nm. If the roughness exceeds 10 nm, it will affect the surface flatness of the upper structure of the quantum well (such as the subsequently grown P-type GaN layer 30), forming voids and affecting device quality; while a roughness less than 1 nm will not effectively release stress in advance.

[0054] S3. An InGaN quantum well active layer 20 is grown on the second structural layer, such that the InGaN quantum well active layer 20 continues the growth pattern of the second structural layer, thereby forming a third structural layer on the surface of the InGaN quantum well active layer 20 with a morphology consistent with the second structural layer. The third structural layer includes multiple opposing protrusions 201 and multiple opposing recesses 202, such as... Figure 3d As shown.

[0055] S4. A P-type GaN layer 30 is grown on the InGaN quantum well active layer 20, and the P-type GaN layer 30 is gradually filled into the third structural layer until the surface of the P-type GaN layer 30 is smooth. Figure 2 As shown.

[0056] The fabrication method provided by this typical implementation scheme avoids the problem of excessively thick epitaxial thickness in the epitaxial structure of traditional GaN-based optoelectronic devices due to the need to improve crystal quality and ensure the quality and luminous efficiency of the light-emitting quantum well. It also eliminates the need for a thicker bottom layer growth from the substrate in heteroepitaxial growth, which will save about 3 to 4 μm of thickness compared with traditional epitaxial structures, making it more suitable for ultra-thin optoelectronic devices (such as Micro-LEDs).

[0057] In this typical implementation, the second and third structural layers can be sawtooth structures, which have the function of V-shaped pits opened by the preparation layer before the growth of the quantum well active layer in traditional epitaxial structures. On the one hand, it can avoid releasing the stress of the quantum well active layer by sacrificing crystal quality (i.e., amplifying dislocations) to form V-shaped pits. On the other hand, it saves the growth of the preparation layer used to open the V-shaped pits, reduces the thickness of the epitaxial structure, and can increase the luminous area of ​​the quantum well, thereby enhancing the luminous efficiency.

[0058] Furthermore, during the fabrication of the epitaxial structure, impurities such as O and C on the surface of the N-type GaN single crystal substrate are removed by in-situ etching, and a first structural layer with uneven surfaces is formed on the surface of the N-type GaN single crystal substrate. Then, by controlling the process parameters, the first structural layer is three-dimensionally grown to form a second structural layer with a roughness of 1-10 nm. Subsequently, a quantum well active layer is epitaxially grown on this second structural layer, so that the growth mode of the quantum well active layer continues that of the second structural layer, thereby forming a quantum well active layer with a third structural layer on the surface. This can release the stress of the quantum well active layer without sacrificing crystal quality, thereby improving the In injection efficiency in the InGaN quantum well active layer and increasing the light-emitting area of ​​the quantum well, which can effectively improve the optoelectronic performance of the optoelectronic device.

[0059] Furthermore, since the quantum well active layer extends the uneven surface of the N-type GaN single crystal substrate, the second structural layer has a similar effect to a V-shaped pit, which can avoid the preparation layer grown in the traditional preparation method to open the V-shaped pit, and can further reduce the thickness of the epitaxial structure.

[0060] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, unless otherwise specified, the preparation processes involved in the following embodiments are all existing processes known to those skilled in the art, and their specific process parameters can be set according to the circumstances, without specific limitations here.

[0061] Example 1:

[0062] An epitaxial structure for optoelectronic devices based on GaN homoepitaxy can be referenced. Figure 2 Its preparation method includes the following steps:

[0063] Step 1) Provide, for example Figure 3a The N-type GaN single crystal substrate 10 is shown, and the N-type GaN single crystal substrate 10 is placed in the reaction chamber of the epitaxial growth system.

[0064] Step 2) Set the temperature in the reaction chamber to 1100℃ and the pressure to 200 torr, and introduce H2 and NH3 to heat-bake and clean the N-type GaN single crystal substrate 10 to remove impurities such as O and C from the surface of the N-type GaN single crystal substrate 10. The duration is 5 minutes. After that, turn off NH3 for about 10-30 seconds and continue to introduce H2 to perform in-situ etching on the surface of the N-type GaN single crystal substrate 10 through H2, thereby forming a first structural layer on the surface of the N-type GaN single crystal substrate 10. The first structural layer includes multiple protruding structures 103, such as... Figure 3b As shown.

[0065] Step 3) The temperature in the reaction chamber is lowered to 900℃, the pressure is increased to 500 torr, and a mixed gas of NH3 (Group V nitrogen source) and TMGa (Group III metal source) with a molar ratio of 500 is introduced. After 5-10 minutes, the first structural layer on the surface of the N-type GaN single crystal substrate 10 is three-dimensionally grown to form the second structural layer. The second structural layer includes multiple relatively protruding portions 101 and multiple relatively recessed portions 102, such as... Figure 3c As shown.

[0066] In this embodiment, by controlling the conditions and growth time, the final total thickness of the first and second structural layers is controlled to be approximately 300 nm.

[0067] In this embodiment, during three-dimensional growth, doping can also be performed by introducing TMI sources, SiH4, etc., as needed.

[0068] Step 4) Grow an InGaN quantum well active layer 20 on the second structural layer, allowing the InGaN quantum well active layer 20 to continue the growth pattern of the second structural layer, thereby forming a third structural layer on the surface of the InGaN quantum well active layer 20 with a roughness close to that of the second structural layer. This third structural layer includes multiple opposing protrusions 201 and multiple opposing recesses 202, such as... Figure 3d As shown.

[0069] Step 5) Grow a P-type GaN layer 30 on the InGaN quantum well active layer 20, allowing the P-type GaN layer 30 to gradually fill the third structural layer, ultimately giving the P-type GaN layer 30 a smooth surface. This completes the process. Figure 2 The fabrication of the optoelectronic device epitaxial structure based on GaN homoepitaxial growth is shown.

[0070] Next, please refer to Figure 4 The image shows the surface morphology of an N-type GaN single-crystal substrate after three-dimensional roughening. This uneven surface morphology can significantly increase the luminescent area of ​​the subsequently grown InGaN quantum well active layer. Raman spectroscopy tests were performed on the N-type GaN single-crystal substrate before and after the three-dimensional roughening treatment, and the results are as follows: Figure 5 As shown, the Raman peaks underwent a blue shift after coarsening, indicating that the N-type GaN single crystal substrate was subjected to tensile stress. This releases the stress in advance for the subsequent growth of the InGaN quantum well active layer, which is beneficial for the injection of its In composition.

[0071] Furthermore, surface roughness testing and analysis revealed that the surface roughness of the N-type GaN single-crystal substrate after three-dimensional roughening in this embodiment is approximately 10 nm. This allows for excellent stress relief in the subsequently grown InGaN quantum well active layer, thereby improving the implantation efficiency of the In component in InGaN. Moreover, testing of the finally fabricated optoelectronic device showed that the emission wavelength can reach up to 600 nm. Figure 6 As shown.

[0072] Example 2:

[0073] The method for fabricating an epitaxial structure of an optoelectronic device based on GaN homoepitaxial growth provided in this embodiment is basically the same as that in Embodiment 1, except that:

[0074] Step 2) Set the temperature in the reaction chamber to 1050℃ and the pressure to 300 torr, and introduce H2 and NH3 to heat-bake and clean the N-type GaN single crystal substrate 10 to remove impurities such as O and C from the surface of the N-type GaN single crystal substrate 10 for 5 minutes. After that, turn off NH3 for about 10-30 seconds and continue to introduce H2 to perform in-situ etching on the surface of the N-type GaN single crystal substrate 10, thereby forming a first structural layer on the surface of the N-type GaN single crystal substrate 10. The first structural layer includes multiple protruding structures 103, such as... Figure 3b As shown.

[0075] Step 3) The temperature in the reaction chamber is lowered to 950℃, the pressure is increased to 400 torr, and a mixed gas of NH3 (Group V nitrogen source) and TMGa (Group III metal source) with a molar ratio of 1000 is introduced. After 5-10 minutes, the first structural layer on the surface of the N-type GaN single crystal substrate 10 is three-dimensionally grown to form the second structural layer. The second structural layer includes multiple relatively protruding portions 101 and multiple relatively recessed portions 102, such as... Figure 3c As shown.

[0076] Surface roughness testing and analysis revealed that the surface roughness of the three-dimensionally grown N-type GaN single-crystal substrate in this embodiment is approximately 1 nm. This allows for relatively good stress relief in the subsequently grown InGaN quantum well active layer, thereby improving the implantation efficiency of the In component in InGaN. Testing of the final fabricated optoelectronic device showed that the emission wavelength can reach 450 nm. Figure 6 As shown.

[0077] Example 3:

[0078] The method for fabricating an epitaxial structure of an optoelectronic device based on GaN homoepitaxial growth provided in this embodiment is basically the same as that in Embodiment 1, except that:

[0079] Step 2) Set the temperature in the reaction chamber to 1080℃ and the pressure to 250 torr, and introduce H2 and NH3 to perform thermal baking and cleaning on the N-type GaN single crystal substrate 10 to remove impurities such as O and C from the surface of the N-type GaN single crystal substrate 10. The duration is 5 minutes. After that, turn off NH3 for about 10-30 seconds and continue to introduce H2 to perform in-situ etching on the surface of the N-type GaN single crystal substrate 10 through H2, thereby forming a first structural layer on the surface of the N-type GaN single crystal substrate 10. The first structural layer includes multiple convex and undulating structures 103, such as... Figure 3b As shown.

[0080] Step 3) The temperature in the reaction chamber is lowered to 920°C, the pressure is increased to 450 torr, and a mixed gas of NH3 (Group V nitrogen source) and TMGa (Group III metal source) with a molar ratio of 800 is introduced. After 5-10 minutes, the first structural layer on the surface of the N-type GaN single crystal substrate 10 is three-dimensionally grown to form the second structural layer. The second structural layer includes multiple relatively protruding portions 101 and multiple relatively recessed portions 102, such as... Figure 3c As shown.

[0081] Surface roughness testing and analysis revealed that the surface roughness of the three-dimensionally grown N-type GaN single-crystal substrate in this embodiment is approximately 6 nm. This allows for relatively good stress relief in the subsequently grown InGaN quantum well active layer, thereby improving the implantation efficiency of the In component in InGaN. Testing of the final fabricated optoelectronic device showed that the emission wavelength can reach 550 nm. Figure 6 As shown.

[0082] Comparative Example 1:

[0083] The method for fabricating an epitaxial structure of an optoelectronic device based on GaN homoepitaxy provided in this comparative example is basically the same as that in Example 1, except that:

[0084] Step 3) Lower the temperature in the reaction chamber to 800℃, raise the pressure to 600 torr, and introduce a mixed gas of NH3 (Group V nitrogen source) and TMGa (Group III metal source) with a molar ratio of 400 for about 5-10 minutes of growth.

[0085] According to surface roughness testing and analysis, the surface roughness of the N-type GaN single crystal substrate grown in this comparative example is about 15nm. Excessive roughness will affect the surface flatness of the upper structure of the quantum well (such as the P-type GaN layer), forming holes and affecting the device quality.

[0086] Comparative Example 2:

[0087] The method for fabricating an epitaxial structure of an optoelectronic device based on GaN homoepitaxy provided in this comparative example is basically the same as that in Example 1, except that:

[0088] Step 3) Continue to set the temperature in the reaction chamber to 1100℃, increase the pressure to 500 torr, and introduce a mixed gas of NH3 (Group V nitrogen source) and TMGa (Group III metal source) with a molar ratio of 500 for about 5-10 minutes of growth.

[0089] Compared with Example 1, in this comparative example, the multiple protruding structures 103 on the surface of the first structural layer of the N-type GaN single crystal substrate will undergo two-dimensional lateral growth and eventually be filled, which will not release the stress of the subsequently grown quantum well active layer. The injection efficiency of the In component will be greatly reduced, and the flat surface of the quantum well active layer will not be able to achieve the effect of increasing the light-emitting area, and the luminous efficiency of the device will also be reduced accordingly.

[0090] Comparative Example 3:

[0091] The method for fabricating an epitaxial structure of an optoelectronic device based on GaN homoepitaxy provided in this comparative example is basically the same as that in Example 1, except that:

[0092] Step 3) Reduce the temperature in the reaction chamber to 900℃, continue to set the pressure to 200 torr, and introduce a mixed gas of NH3 (Group V nitrogen source) and TMGa (Group III metal source) with a molar ratio of 500 for about 5-10 minutes of growth.

[0093] Compared with Example 1, in this comparative example, the multiple protruding structures 103 on the surface of the first structural layer of the N-type GaN single crystal substrate will undergo two-dimensional lateral growth and eventually be filled, which will not release the stress of the subsequently grown quantum well active layer. The injection efficiency of the In component will be greatly reduced, and the flat surface of the quantum well active layer will not be able to achieve the effect of increasing the light-emitting area, and the luminous efficiency of the device will also be reduced accordingly.

[0094] It should be understood that the technical solutions of the present invention are not limited to the specific embodiments described above. Any technical modifications made to the technical solutions of the present invention without departing from the spirit and scope of the claims are within the scope of protection of the present invention.

Claims

1. A method for fabricating an epitaxial structure of an optoelectronic device, characterized in that, The method comprises the following steps: S1. cleaning the surface of an N-type single crystal substrate under a hydrogen and NH3 atmosphere at a first process parameter, and performing in-situ etching on the surface by using the opening of NH3 to form a first structure layer with a concave-convex morphology on the surface of the N-type single crystal substrate; S2. performing three-dimensional growth on the first structure layer at a second process parameter to form a second structure layer with a roughness of 1-10 nm, and the roughness of the second structure layer is greater than that of the first structure layer; wherein the first process parameter at least comprises a first temperature, and the second process parameter at least comprises a second temperature, and the second temperature is lower than the first temperature; S3. growing a quantum well active layer on the second structure layer, and making the quantum well active layer continue the growth mode of the second structure layer to form a third structure layer on the upper surface of the quantum well active layer, and the roughness of the third structure layer is not greater than that of the second structure layer; S4. growing a P-type semiconductor layer on the quantum well active layer, and making the surface of the P-type semiconductor layer flat.

2. The method of claim 1, wherein the method further comprises: The step S1 specifically comprises: adjusting the temperature to the first temperature under a hydrogen atmosphere, and opening NH3 for at least 5 min to perform thermal cleaning on the surface of the N-type single crystal substrate; and then alternately opening and closing NH3, and the closing time is 10-30 s to perform in-situ etching on the surface of the N-type single crystal substrate; wherein the first temperature is 1050-1100 ℃.

3. The method of claim 1, wherein the method further comprises: The first process parameter further comprises a first pressure, and the second process parameter further comprises a second pressure; the first pressure is less than the second pressure; and the second pressure is 400-500 torr.

4. The method of claim 1, wherein the method further comprises: The second process parameter further comprises a V / III value; and the step S2 specifically comprises: controlling the V / III value to be 500-1000 under the second temperature condition to perform three-dimensional growth on the first structure layer, wherein the time of the three-dimensional growth is 5-10 min, and the second temperature is 900-950 ℃.

5. The method of claim 1, wherein the method further comprises: The step S2 specifically further comprises: introducing N-type doping when performing the three-dimensional growth, and the N-type doping comprises a TMIn source and SiH4.

6. The method of claim 1, wherein the epitaxial structure is a photovoltaic device. Specifically comprising: continuously performing the steps S1-S4 in the same reaction chamber.

7. An epitaxial structure for an optoelectronic device, characterized in that Comprise: an N-type single crystal substrate; the surface of the N-type single crystal substrate has a first structure layer formed by in-situ etching and a second structure layer formed by three-dimensional roughening growth on the first structure layer, the roughness of the second structure layer is 1-10 nm, which is greater than that of the first structure layer; and the second structure layer comprises a plurality of relatively convex parts and a plurality of relatively concave parts; a quantum well active layer; the quantum well active layer is formed on the second structure layer, and it continues the growth mode of the second structure layer to form a third structure layer on the upper surface of the quantum well active layer, and the roughness of the third structure layer is not greater than that of the second structure layer; the third structure layer comprises a plurality of relatively convex parts and a plurality of relatively concave parts; a P-type semiconductor layer; the P-type semiconductor layer is formed on the quantum well active layer, and the surface of the P-type semiconductor layer is flat.

8. The epitaxial structure of claim 7, wherein: The total thickness of the first and second structure layers is 100-300 nm.

9. The epitaxial structure of claim 7, wherein: The thickness of the epitaxial structure is 1-2 μm.

10. The epitaxial structure of claim 7, wherein: The N-type single crystal substrate comprises an N-type GaN single crystal substrate.

11. An optoelectronic device, characterized by An epitaxial structure comprising the optoelectronic device of any one of claims 7-10.

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