Epitaxial wafer of LED device and its preparation method

Abstract

The present invention discloses an epitaxial wafer for an LED device and a preparation method thereof. The epitaxial wafer for the LED device includes: a substrate, a nucleation layer, and an epitaxial structure layer. The surface of the substrate has a first region and a second region adjacent to the first region; the nucleation layer is disposed on the first region; the epitaxial structure layer includes a first light-emitting unit and a second light-emitting unit. The first light-emitting unit is disposed on the nucleation layer, and the second light-emitting unit is disposed on the second region of the substrate surface. Among them, the first light-emitting unit is mainly composed of a Ga-face group III nitride material, and the second light-emitting unit is mainly composed of an N-face group III nitride material. By adopting the present invention, the light-emitting efficiency of the LED device is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductors, and particularly relates to an epitaxial wafer of a white light LED device with a dual-color active layer and a preparation method thereof. Background Art

[0002] At present, there are two technical approaches to achieve white light illumination using light-emitting diodes (LEDs): one is to use LEDs to excite fluorescent substances to form white light, which can be called "secondary light conversion white light technology"; the other is to use LEDs to directly emit white light, which can be called "direct emission white light technology". "Secondary light conversion white light technology" mainly uses blue LEDs to excite yellow phosphors, and the yellow light emitted by the excited yellow phosphors is mixed with the blue light emitted by the LEDs to form white light, as Figure 1 shown; this technical method is simple, practical, and has good temperature stability, but the color temperature is relatively high, the color rendering property is poor, and the color uniformity is related to the angle. "Direct emission white light technology" uses nitride LEDs to directly emit white light without the need for fluorescent substances, eliminating the limitations of the light conversion efficiency and service life of fluorescent substances on the performance of solid-state lighting sources.

[0003] At present, "direct emission white light technology" can be implemented in two ways: multi-chip type and single-chip type. The multi-chip type scheme is as Figure 2 shown, which is to package three LED chips emitting red, green, and blue light on a substrate and use the three colors to mix into white light. The disadvantage of this scheme is the low integration and high cost. The single-chip type scheme is to use a multi-active layer stacked quantum well LED structure on a single chip to emit multi-color light to synthesize white light. The typical structure of a single-chip dual-active layer dual-color LED device is as Figure 3 shown. The active layer is a 5-period InGaN / GaN multi-quantum well, and different In compositions are used to emit blue light with a wavelength of 460 nm and green light with a wavelength of 520 nm respectively, and white light is obtained without the need for fluorescent substances. Figure 4 is the emission spectrum of a typical blue / yellow single-chip dual-active layer LED device. At present, this scheme is the mainstream technical scheme in "direct emission white light technology".

[0004] However, the disadvantages of the monolithic dual-active-layer dual-color LED device include: First, due to the different In compositions of InGaN in the two active layers and different bandgaps, the InGaN with a higher In composition (emitting light with a longer wavelength, such as yellow light) has a smaller bandgap and will strongly absorb short-wavelength light (such as blue light); in the conventional device structure, the short-wavelength light emitted downward by the quantum well will be reflected by the substrate and emerge from the device surface again; however, in this dual-active-layer dual-color LED device, the downward-emitted blue light will be absorbed during the process of passing through the active layer emitting yellow light, thus reducing the final light extraction efficiency of the device; Second, in this scheme, when fabricating the device, the quantum well structure with a long wavelength (such as yellow light) is placed below, and the quantum well structure with a short wavelength (such as blue light) is placed above. During the growth process of the quantum well structure with a short wavelength (such as blue light), its growth temperature is usually higher than that of the quantum well structure with a long wavelength. Increasing the temperature will cause the decomposition of the InGaN material, so the performance of the quantum well structure with a long wavelength will degenerate, affecting the device performance. Summary of the Invention

[0005] The main object of the present invention is to provide an epitaxial wafer of an LED device and a preparation method thereof, so as to overcome the deficiencies in the prior art.

[0006] To achieve the foregoing invention object, the technical solutions adopted by the present invention include:

[0007] On the one hand, the present invention provides an epitaxial wafer of an LED device, including:

[0008] A substrate, the surface of the substrate having a first region and a second region adjacent to the first region;

[0009] A nucleation layer, disposed in the first region;

[0010] An epitaxial structure layer, including a first light-emitting unit and a second light-emitting unit, the first light-emitting unit being disposed on the nucleation layer, the second light-emitting unit being disposed in the second region, wherein the first light-emitting unit includes a Ga-face group III nitride material, and the second light-emitting unit includes an N-face group III nitride material.

[0011] Further, the first light-emitting unit includes a Ga-face n-type semiconductor layer, a Ga-face light-emitting layer, a Ga-face electron blocking layer, and a Ga-face p-type semiconductor layer that are sequentially stacked on the nucleation layer, and the second light-emitting unit includes an N-face n-type semiconductor layer, an N-face light-emitting layer, an N-face electron blocking layer, and an N-face p-type semiconductor layer that are sequentially stacked on the second region.

[0012] Among them, the Ga-face n-type semiconductor layer and the N-face n-type semiconductor layer, the Ga-face light-emitting layer and the N-face light-emitting layer, the Ga-face electron blocking layer and the N-face electron blocking layer, and the Ga-face p-type semiconductor layer and the N-face p-type semiconductor layer are all integrally formed.

[0013] Furthermore, the In component content in the Ga-face light-emitting layer is less than the In component content in the N-face light-emitting layer.

[0014] Furthermore, the Ga-face light-emitting layer and the N-face light-emitting layer are located in the same plane.

[0015] Furthermore, the Ga-face n-type semiconductor layer and the N-face n-type semiconductor layer, the Ga-face electron blocking layer and the N-face electron blocking layer, and the Ga-face p-type semiconductor layer and the N-face p-type semiconductor layer are also respectively located in the same plane.

[0016] Furthermore, the epitaxial wafer further includes a buffer layer, the buffer layer includes an integrally formed Ga-face buffer layer and an N-face buffer layer, the Ga-face buffer layer is disposed between the nucleation layer and the first light-emitting unit, and the N-face buffer layer is disposed between the second region and the second light-emitting unit, wherein the material of the buffer layer can be GaN.

[0017] Furthermore, the top surfaces of the Ga-face buffer layer and the N-face buffer layer facing away from the substrate are flush.

[0018] Furthermore, the n-type semiconductor layer can be an n-type GaN layer, the light-emitting layer can be an InGaN / GaN multiple quantum well light-emitting layer, the electron blocking layer can be an AlGaN electron blocking layer, and the p-type semiconductor layer can be a p-type GaN layer; specifically, the light-emitting layer can also be referred to as an active layer, an active region, etc.

[0019] Furthermore, the substrate can be a sapphire substrate or a silicon carbide substrate, etc. Preferably, the substrate is a sapphire substrate with a bevel angle, the bevel angle direction of the sapphire substrate is c-plane offset m-axis, and the bevel angle is 1 to 4°.

[0020] Furthermore, the material of the nucleation layer includes group III nitrides. Exemplarily, the nucleation layer can be an AlN nucleation layer or a GaN nucleation layer, etc.

[0021] On the other hand, the present invention also provides a method for preparing an epitaxial wafer of an LED device, including:

[0022] Providing a substrate, the surface of the substrate having a first region and a second region adjacent to the first region;

[0023] Forming a nucleation layer in the first region;

[0024] An epitaxial structure layer is formed on the nucleation layer. The epitaxial structure layer includes a first light-emitting unit and a second light-emitting unit. The first light-emitting unit is disposed on the nucleation layer, and the second light-emitting unit is disposed on the second region. Wherein, the first light-emitting unit includes a Ga-face group III nitride material, and the second light-emitting unit includes an N-face group III nitride material.

[0025] Further, the step of forming the epitaxial structure layer on the nucleation layer includes:

[0026] Growing a group III nitride material on the surface of the nucleation layer and the second region simultaneously, and during the growth of the group III nitride material, adjusting the growth parameters of the group III nitride material so that the group III nitride material grown on the nucleation layer forms a Ga-face group III nitride material, and the group III nitride material grown on the second region forms an N-face group III nitride material. Wherein, the growth parameters include at least one of growth temperature, growth pressure, and V-III ratio of the growth raw material.

[0027] It can be understood that the V-III ratio is the molar ratio of a group V element to a group III element.

[0028] Further, the first light-emitting unit includes a Ga-face n-type semiconductor layer, a Ga-face light-emitting layer, a Ga-face electron blocking layer, and a Ga-face p-type semiconductor layer that are sequentially stacked on the nucleation layer. The second light-emitting unit includes an N-face n-type semiconductor layer, an N-face light-emitting layer, an N-face electron blocking layer, and an N-face p-type semiconductor layer that are sequentially stacked on the second region. Wherein, the Ga-face n-type semiconductor layer and the N-face n-type semiconductor layer, the Ga-face light-emitting layer and the N-face light-emitting layer, the Ga-face electron blocking layer and the N-face electron blocking layer, and the Ga-face p-type semiconductor layer and the N-face p-type semiconductor layer are integrally formed. The step of forming the epitaxial structure layer on the nucleation layer specifically includes:

[0029] Growing the Ga-face n-type semiconductor layer and the N-face n-type semiconductor layer under a first preset condition. The first preset condition includes: the growth temperature is 1000 - 1100 °C, the growth pressure is 100 - 400 mbar, and the V-III ratio of the growth raw material is 500 - 2000.

[0030] Growing the Ga-face light-emitting layer and the N-face light-emitting layer under a second preset condition. The second preset condition includes: the growth temperature is 700 - 900 °C, the growth pressure is 100 - 400 mbar, and the V-III ratio of the growth raw material is 10000 - 30000.

[0031] The growth of the Ga-face electron blocking layer and the N-face electron blocking layer is carried out under a third preset condition, and the third preset condition includes: the growth temperature is 1000-1100 °C, the growth pressure is 100-200 mbar, and the V-III ratio of the growth raw material is 500-2000;

[0032] The growth of the Ga-face p-type semiconductor layer and the N-face p-type semiconductor layer is carried out under a fourth preset condition, and the fourth preset condition includes: the growth temperature is 1000-1100 °C, the growth pressure is 100-400 mbar, and the V-III ratio of the growth raw material is 500-2000.

[0033] Further, the step of forming the epitaxial structure layer on the nucleation layer further includes:

[0034] A buffer layer is formed on the nucleation layer and the second region, and a flat surface is formed on the top of the grown buffer layer;

[0035] The epitaxial structure layer is grown on the buffer layer.

[0036] Further, the buffer layer includes a Ga-face buffer layer and an N-face buffer layer, and the step of forming the buffer layer on the nucleation layer and the second region includes:

[0037] The Ga-face buffer layer and the N-face buffer layer are grown simultaneously under a fifth preset condition, so that the top surfaces of the Ga-face buffer layer and the N-face buffer layer are flush. The fifth preset condition includes: the growth temperature is 1050-1150 °C, the growth pressure is 100-400 mbar, and the V-III ratio of the growth raw material is 100-1000; Exemplarily, the material of the buffer layer can be GaN.

[0038] Further, the preparation method specifically includes: forming a nucleation layer in the first region, removing the nucleation layer covering the second region to expose the second region; or, covering a mask on the second region; forming a nucleation layer in the first region; removing the mask to expose the second region.

[0039] Further, the substrate can be a sapphire substrate or a silicon carbide substrate, etc. Preferably, the sapphire substrate is a sapphire substrate with an oblique cut angle, and the oblique cut angle direction of the sapphire substrate is c-plane biased m-axis, and the oblique cut angle is 1-4°.

[0040] Further, the material of the nucleation layer includes group III nitrides. Exemplarily, the nucleation layer can be an AlN nucleation layer or a GaN nucleation layer, etc.

[0041] Compared with the prior art, the advantages of the present invention include:

[0042] 1) The Ga-face active layer and the N-face active layer obtained by the method for preparing an epitaxial wafer of an LED device in the present invention are disposed on the same plane. During the light extraction process, there is no physical process in which short-wavelength light passes through a long-wavelength quantum well and is absorbed. Therefore, the light-emitting efficiency of the device is improved.

[0043] 2) By controlling the area ratio of the nucleation layer to be etched and the nucleation layer to be retained in the present invention, the area ratio of the Ga-face group-III nitride material and the N-face group-III nitride material can be controlled, thereby realizing the control of the area ratio of the first light-emitting unit and the second light-emitting unit, and further controlling the ratio of the light-emitting areas of the two wavelengths of light emitted by the light-emitting unit. Finally, white light illumination is achieved by obtaining white light that meets the requirements. Description of the Drawings

[0044] Figure 1 is a schematic diagram of realizing white light illumination by using a blue LED and a yellow phosphor in the prior art;

[0045] Figure 2 is a schematic diagram of realizing white light illumination by using red, green, and blue LEDs in the prior art;

[0046] Figure 3 is a schematic structural diagram of a monolithic dual-active-layer dual-color LED structure in the prior art;

[0047] Figure 4 is the emission spectrum of a monolithic dual-active-layer dual-color LED device in the prior art;

[0048] Figure 5 is a comparison curve of the emission wavelengths of the Ga-face InGaN material and the N-face InGaN material;

[0049] Figure 6 is a schematic structural diagram of an epitaxial wafer of a white LED device with a dual-color active layer provided by the present invention;

[0050] Figures 7a - 7f is a schematic process diagram of preparing an epitaxial wafer of a white LED device with a dual-color active layer provided by the present invention;

[0051] Figure 8 is an emission spectrum diagram of an LED device integrating Ga-face and N-face InGaN / GaN quantum well structures provided by the present invention. Detailed Embodiments

[0052] In view of the deficiencies in the prior art, through long-term research and a large number of practices, the inventors of this case have been able to propose the technical solution of the present invention. The following will further explain the technical solution, its implementation process and principles in combination with the accompanying drawings and specific implementation cases. Unless otherwise specified, the Metal-organic Chemical Vapor Deposition (MOCVD) equipment, Physical Vapor Deposition (PVD) equipment, Reactive Ion Etching (RIE) equipment, and nitrogen source, group III source, carrier gas, etc. used in the embodiments of the present invention for growing epitaxial structure layers are all known to those skilled in the art and will not be elaborated here.

[0053] The inventors of this case have found through research that the emission wavelength of GaN-based LED devices is determined by the In composition of the InGaN quantum wells in the devices. The higher the In composition, the longer the emission wavelength. Since GaN is a polar semiconductor, Ga-face GaN materials and N-face GaN materials can be obtained respectively by controlling the growth process. Currently, the main Ga-face GaN materials are used in devices such as LEDs. Due to the difference in polarity, at the same growth temperature, compared with Ga-face GaN materials, the In composition of the InGaN materials grown on N-face GaN materials is higher. Figure 5 It can be seen that the emission wavelength corresponding to the InGaN materials grown on N-face GaN materials is longer. Among them, "N-polar" is the N-face and "Ga-polar" is the Ga-face. The present invention simultaneously grows Ga-face GaN / InGaN quantum well materials and N-face GaN / InGaN quantum well materials on the same substrate, so that the quantum well structures in GaN-based LED devices emit two different wavelengths of light simultaneously, thereby obtaining a monolithic dual-color white LED device. It should be noted that the light emitted by the device has a certain divergence angle, which can mix the two different wavelengths of light to form white light.

[0054] Embodiment 1

[0055] Please refer to Figure 6 , Figure 6 which is a schematic structural diagram of an epitaxial wafer of an LED device provided by the present invention. The epitaxial wafer includes a sapphire substrate 100, an AlN nucleation layer 200, a GaN buffer layer, and an epitaxial structure layer.

[0056] The surface of the sapphire substrate 100 has a first region and a second region adjacent to the first region. Specifically, the sapphire substrate 100 is a sapphire substrate with a bevel angle. The bevel angle direction of the sapphire substrate is c-plane biased towards the m-axis, and the bevel angle is 1 to 4°.

[0057] The AlN nucleation layer 200 is disposed in a first region on the surface of the sapphire substrate 100, and the GaN buffer layer is disposed on the surface of the AlN nucleation layer 200 and a second region on the surface of the sapphire substrate 100.

[0058] The GaN buffer layer includes a Ga-face GaN buffer layer 310 and an N-face GaN buffer layer 320 formed integrally; the Ga-face GaN buffer layer 310 is stacked on the AlN nucleation layer 200, and the N-face GaN buffer layer 320 is stacked on a second region on the surface of the sapphire substrate 10. Further, the Ga-face GaN buffer layer 310 is a Ga-polarity GaN buffer layer composed of Ga-face GaN material, and the N-face GaN buffer layer 320 is an N-polarity GaN buffer layer composed of N-face GaN material.

[0059] Further, the surface of the GaN buffer layer is continuous and flat, that is, the top surfaces (i.e., the side away from the sapphire substrate 100) of the Ga-face GaN buffer layer 310 and the N-face GaN buffer layer 320 are continuous and flat; specifically, since the AlN nucleation layer 200 is disposed between the Ga-face GaN buffer layer 310 and the sapphire substrate 100, the thickness of the Ga-face GaN buffer layer 310 is less than the thickness of the N-face GaN buffer layer 320, and the sum of the thicknesses of the Ga-face GaN buffer layer 310 and the AlN nucleation layer 200 is equal to the thickness of the N-face GaN buffer layer 320; by way of example, the thickness of the AlN nucleation layer 200 is 100 nm, the thickness of the Ga-face GaN buffer layer 310 is 400 nm, and the thickness of the N-face GaN buffer layer 320 is 500 nm. In this embodiment, the AlN nucleation layer 200 grown on the sapphire substrate 100 is the Al face (metal face), and the GaN buffer layer grown on the AlN nucleation layer 200 is the Ga-face GaN buffer layer 310; the N-face GaN buffer layer 320 is directly grown on the sapphire substrate 100 by controlling the growth conditions, without affecting the polarity of the Ga-face GaN buffer layer 310 on the AlN nucleation layer 200.

[0060] The epitaxial structure layer includes an n-type GaN layer, an InGaN / GaN multiple quantum well (MQW) light-emitting layer, an AlGaN electron-blocking layer (EBL), and a p-type GaN layer stacked in sequence on the GaN buffer layer.

[0061] Specifically, the n-type GaN layer includes an integrally formed Ga-face n-type GaN layer 411 and an N-face n-type GaN layer 421; the InGaN / GaN multiple quantum well light-emitting layer includes an integrally formed Ga-face InGaN / GaN multiple quantum well layer (i.e., Ga-face active layer or Ga-face light-emitting layer) 412 and an N-face InGaN / GaN multiple quantum well layer (i.e., N-face active layer or N-face light-emitting layer) 422; the AlGaN electron blocking layer includes an integrally formed Ga-face AlGaN electron blocking layer 413 and an N-face AlGaN electron blocking layer 423; the p-type GaN layer includes an integrally formed Ga-face p-type GaN layer 414 and an N-face p-type GaN layer 424.

[0062] Further, the Ga-face n-type GaN layer 411, the Ga-face InGaN / GaN multiple quantum well layer 412, the Ga-face AlGaN electron blocking layer 413, and the Ga-face p-type GaN layer 414 are sequentially stacked on the Ga-face GaN buffer layer 310 and constitute a first light-emitting unit 410; the N-face n-type GaN layer 421, the N-face InGaN / GaN multiple quantum well layer 422, the N-face AlGaN electron blocking layer 423, and the N-face p-type GaN layer 424 are sequentially stacked on the N-face GaN buffer layer 320 and constitute a second light-emitting unit 420.

[0063] Further, the Ga-face n-type GaN layer 411 and the N-face n-type GaN layer 421 are formed simultaneously and have the same thickness; the Ga-face InGaN / GaN multiple quantum well layer 412 and the N-face InGaN / GaN multiple quantum well layer 422 are formed simultaneously and have the same thickness; the Ga-face AlGaN electron blocking layer 413 and the N-face AlGaN electron blocking layer 423 are formed simultaneously and have the same thickness; the Ga-face p-type GaN layer 414 and the N-face p-type GaN layer 424 are formed simultaneously and have the same thickness, and the content of the In component in the Ga-face InGaN / GaN multiple quantum well layer 412 is less than the content of the In component in the N-face InGaN / GaN multiple quantum well layer 422.

[0064] The solution provided by the present invention can realize the integration of dual InGaN active layers with different In components on the same substrate. Compared with the monolithic dual-active-layer dual-color LED structure in the traditional technical solution (as Figure 3 shown), the epitaxial wafer of the LED device provided by the present invention not only has dual-color active layers to emit white light, but also these two active layers are at the same height. Therefore, there is no phenomenon that short-wavelength light passes through the long-wavelength active layer and is absorbed during the light extraction process, thereby improving the light extraction efficiency of the LED device and further improving the luminous efficiency of the LED device.

[0065] Please refer to Figures 7a - 7f , Figures 7a - 7fA method for preparing an epitaxial wafer of an LED device provided by the present invention, the method comprising the following steps:

[0066] 1) Provide a sapphire substrate 100, as Figure 7a shown.

[0067] In order to improve the surface morphology of the N-face GaN material, the present invention uses a beveled sapphire substrate with a bevel angle direction of c-plane offset from the m-axis and a bevel angle of 1 to 4°.

[0068] 2) Form an AlN nucleation layer 200 in a first region on the surface of the sapphire substrate 100, as Figure 7b shown.

[0069] Step 2) may specifically include:

[0070] 2.1) Place the sapphire substrate 100 in the reaction chamber of an MOCVD device, raise the temperature in the reaction chamber to 1100°C, adjust the pressure to 130 mbar, use hydrogen as the carrier gas, introduce TMAl and NH3 into the reaction chamber, and control the introduction flow rate of TMAl to be 100 sccm and the introduction flow rate of NH3 to be 1000 sccm to grow an AlN nucleation layer 200 with a thickness of 100 nm on the surface of the sapphire substrate 100.

[0071] In one embodiment, the AlN nucleation layer 200 may be a high-temperature AlN nucleation layer. The high-temperature AlN nucleation layer can obtain high-quality Ga-face GaN material, and the use of an etching process (such as: RIE) can well remove the high-temperature AlN nucleation layer, prevent the high-temperature AlN nucleation layer from remaining in the second region on the surface of the sapphire substrate, ensure that the high-temperature AlN nucleation layer is only provided in the first region on the surface of the sapphire substrate 100, and thus ensure the quality of the device.

[0072] 2.2) Lower the temperature in the reaction chamber to room temperature, coat a photoresist on the AlN nucleation layer 200 and expose the photoresist above a part of the AlN nucleation layer 200 through a photolithography process, and retain the photoresist on a part of the AlN nucleation layer 200; then use a reactive ion etching process to etch away the AlN nucleation layer 200 in other regions, so as to expose the second region on the surface of the sapphire substrate 100.

[0073] The etching gas used in the reactive ion etching process is Cl2, the radio frequency power is 60 W, the pressure is 10 mTorr, the gas flow rate is 15 sccm, the etching thickness is 120 nm, and the retained AlN nucleation layer 200 is coated on the first region on the surface of the sapphire substrate 100.

[0074] It should be noted that in another embodiment, step 2) may further include: first growing a mask layer on the surface of the sapphire substrate 100, and the material of the mask layer may be SiO2 or SiN x ; then, the mask layer in the first region on the surface of the sapphire substrate 100 is processed through photolithography and etching processes to remove the mask layer in the first region; then, an AlN nucleation layer 200 is grown on the first region by using the MOCVD method, and then the mask layer in the remaining region (i.e., the second region) is removed.

[0075] It should be noted that in other embodiments, the AlN nucleation layer may also be grown by using a magnetron sputtering method.

[0076] 3) A GaN buffer layer is grown on the second region on the surface of the sapphire substrate 100 and the AlN nucleation layer 200. The GaN buffer layer includes a Ga-face GaN buffer layer 310 and an N-face GaN buffer layer 320 formed integrally, as Figure 7c shown.

[0077] The sapphire substrate 100 with the AlN nucleation layer 200 covered in the first region is placed back into the reaction chamber of the MOCVD equipment. The temperature in the reaction chamber is adjusted to 1050 °C and the pressure is adjusted to 260 mbar. Using hydrogen as the carrier gas, TMGa and NH3 are introduced into the reaction chamber. The introduced flow rate of TMGa is controlled to be 240 sccm, and the introduced flow rate of NH3 is controlled to be 30000 sccm to grow an unintentionally doped GaN material on the second region and the AlN nucleation layer 200. Among them, the growth rate of the GaN material on the AlN nucleation layer is less than the growth rate of the GaN material on the second region on the surface of the sapphire substrate, so that the finally formed GaN buffer layer has a flat top surface. Specifically, the GaN material grown on the AlN nucleation layer 200 is the Ga-face GaN buffer layer 310, and the GaN material grown on the sapphire substrate 100 is the N-face GaN buffer layer 320. The thickness of the Ga-face GaN buffer layer 310 in the GaN buffer layer is 400 nm, and the thickness of the N-face GaN buffer layer 320 in the GaN buffer layer is 500 nm.

[0078] Furthermore, by controlling parameters such as the growth temperature, V-III ratio, and growth pressure of the GaN material, the growth rates of the Ga-face GaN buffer layer and the N-face GaN buffer layer can be better controlled, so as to generate flat Ga-face GaN buffer layer and N-face GaN buffer layer, and further obtain high-quality LED devices.

[0079] 4) An n-type GaN layer is grown on the GaN buffer layer. The n-type GaN layer includes a Ga-face n-type GaN layer 411 and an N-face n-type GaN layer 421 formed integrally, as Figure 7d shown.

[0080] Maintain the temperature in the reaction chamber at 1050 °C and the pressure at 260 mbar. Using hydrogen as the carrier gas, introduce TMGa, NH3, and SiH4 into the reaction chamber. Control the flow rate of TMGa introduced to be 240 sccm, the flow rate of NH3 introduced to be 30000 sccm, and the flow rate of SiH4 introduced to be 100 sccm to grow an n-type GaN material on the GaN buffer layer, thereby forming an n-type GaN layer with a thickness of 2500 nm. Specifically, the n-type GaN material grown on the Ga-face GaN buffer layer 310 in the GaN buffer layer is the Ga-face n-type GaN layer 411, and the n-type GaN material grown on the N-face GaN buffer layer 320 in the GaN buffer layer is the N-face n-type GaN layer 421.

[0081] 5) Grow an InGaN / GaN multiple quantum well on the n-type GaN layer. This InGaN / GaN multiple quantum well layer includes an integrally formed Ga-face InGaN / GaN multiple quantum well layer 412 and an N-face InGaN / GaN multiple quantum well layer 422, as Figure 7e shown.

[0082] Adjust the temperature in the reaction chamber to 900 °C and the pressure to 400 mbar. Using N2 as the carrier gas, introduce TMGa, TMIn, and NH3 into the reaction chamber to alternately grow three periods of InGaN well layers and GaN barrier layers on the n-type GaN layer. Specifically, when growing the InGaN well layer, the flow rate of TMGa introduced is 240 sccm, the flow rate of TMIn introduced is 100 sccm, the flow rate of NH3 introduced is 30000 sccm, and the thickness of the InGaN well layer is 3 nm; when growing the GaN barrier layer, the flow rate of TMGa introduced is 240 sccm, the flow rate of NH3 introduced is 30000 sccm, and the thickness of the GaN barrier layer is 2 nm; correspondingly, the InGaN / GaN multiple quantum well material grown on the Ga-face n-type GaN layer 411 is the Ga-face InGaN / GaN multiple quantum well layer 412, and the InGaN / GaN multiple quantum well material grown on the N-face n-type GaN layer 421 is the N-face InGaN / GaN multiple quantum well layer 422, and the content of the In component in the Ga-face InGaN / GaN multiple quantum well layer 412 is less than the content of the In component in the N-face InGaN / GaN multiple quantum well layer 422.

[0083] 6) Grow an AlGaN electron blocking layer on the InGaN / GaN multiple quantum well layer. The AlGaN electron blocking layer includes an integrally formed Ga-face AlGaN electron blocking layer 413 and an N-face AlGaN electron blocking layer 423, as Figure 7f shown.

[0084] Adjust the temperature in the reaction chamber to 1050 °C and the pressure to 200 mbar. Using hydrogen as the carrier gas, introduce TMGa, TMAl, and NH3 into the reaction chamber. Control the flow rate of TMGa to be 100 sccm, the flow rate of TMAl to be 30 sccm, and the flow rate of NH3 to be 30000 scc to grow AlGaN material on the InGaN / GaN multi-quantum well layer, thereby forming an AlGaN electron blocking layer with a thickness of 200 nm. Correspondingly, the AlGaN material grown on the Ga-face InGaN / GaN multi-quantum well layer 412 is the Ga-face AlGaN electron blocking layer 413, and the AlGaN material grown on the N-face InGaN / GaN multi-quantum well layer 422 is the N-face AlGaN electron blocking layer 423.

[0085] 7) Grow a p-type GaN layer on the AlGaN electron blocking layer. The p-type GaN layer includes a Ga-face p-type GaN layer 414 and an N-face p-type GaN layer 424 formed integrally, as Figure 6 shown.

[0086] Adjust the temperature in the reaction chamber to 1050 °C and the pressure to 260 mbar. Using N2 as the carrier gas, introduce TMGa, NH3, and Cp2Mg into the reaction chamber. Control the flow rate of TMGa to be 240 sccm, the flow rate of NH3 to be 30000 sccm, and the flow rate of Cp2Mg to be 10 sccm to grow p-type GaN material on the AlGaN electron blocking layer, thereby forming a p-type GaN layer with a thickness of 200 nm. Correspondingly, the p-type GaN material grown on the Ga-face AlGaN electron blocking layer 413 is the Ga-face p-type GaN layer 414, and the p-type GaN material grown on the N-face AlGaN electron blocking layer 423 is the N-face p-type GaN layer 424.

[0087] 8) Maintain the introduction of N2 and NH3 into the reaction chamber of the MOCVD equipment, adjust the flow rate of NH3 to 30000 scc, adjust the pressure in the reaction chamber to 260 mbar to activate the p-type GaN, and then lower the temperature of the reaction chamber to room temperature and take out the grown epitaxial wafer.

[0088] In a specific embodiment, the emission spectrum of the white light LED device obtained based on the epitaxial wafer of a white light LED device with a dual-color active layer provided by the present invention is as Figure 8 shown. The abscissa in the figure is the emission wavelength, and the ordinate is the normalized emission intensity; from Figure 8 it can be seen that the wavelengths of the two lights are about 450 nm and 550 nm respectively, so that white light can be emitted by superposition, and the emission spectra of the two lights present good Gaussian curves, indicating that the white light LED device prepared by this method has good emission characteristics.

[0089] The solution provided by the present invention has the following advantages:

[0090] 1) A method for preparing an epitaxial wafer of an LED device provided by the present invention, by using an obliquely cut sapphire substrate and controlling the growth conditions, successfully obtains a flat material surface, making the surface of the N-face GaN buffer layer relatively smooth (usually the surface morphology of the N-face GaN is poor, resulting in a low light emission efficiency of the N-face quantum well. The present invention makes the N-face GaN surface smooth and flat by controlling the growth conditions and using an obliquely cut sapphire substrate, etc., thereby improving the light emission characteristics of the quantum well), which helps to improve the light emission efficiency of the N-face GaN / InGaN multiple quantum well layer, and high-quality optoelectronic devices such as LEDs and electronic devices such as HEMTs can be prepared based on this smooth surface, having practical application value.

[0091] 2) The present invention simultaneously grows GaN materials on the substrate and the nucleation layer, realizing the simultaneous acquisition of Ga-face group III nitride materials and N-face group III nitride materials on the same substrate, and realizing the preparation of a device with a mixed polarity based on Ga-face GaN materials and N-face GaN materials; moreover, by utilizing the differences in the characteristics of Ga-face group III nitride materials and N-face group III nitride materials, the In components in the Ga-face GaN / InGaN multiple quantum well layer and the N-face GaN / InGaN multiple quantum well layer are different, obtaining multiple quantum well layers with different emission wavelengths, realizing the integration of two emission wavelengths on the same substrate, and improving the light emission characteristics of the device.

[0092] 3) A method for preparing an epitaxial wafer of a white light LED device with a dual-color active layer provided by the present invention, the obtained Ga-face active layer and N-face active layer are located on the same plane, and there is no physical process in which short-wavelength light passes through the long-wavelength multiple quantum well layer and is absorbed during the light extraction process, ensuring that the light emissions of the two wavelengths do not affect each other, so the light emission efficiency of the device is improved. At the same time, by controlling the area ratio of the etched and remaining nucleation layer, the area ratio of the Ga-face group III nitride material and the N-face group III nitride material (i.e., controlling the area ratio of the first light-emitting unit and the second light-emitting unit) can be controlled, thereby controlling the ratio of the light-emitting areas of the two wavelengths, realizing the control of the light emission intensities of different emission wavelengths, and further obtaining the required dual-color light, and finally realizing white light illumination.

[0093] It should be understood that the above embodiments are only used to illustrate the technical concept and characteristics of the present invention, and their purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and should not be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. An epitaxial wafer of an LED device, characterized in that, Comprising: A substrate, the surface of the substrate having a first region and a second region adjacent to the first region; A nucleation layer disposed in the first region; An epitaxial structure layer including a first light-emitting unit and a second light-emitting unit, the first light-emitting unit being disposed on the nucleation layer, the second light-emitting unit being disposed in the second region, wherein the first light-emitting unit includes a Ga-face group III nitride material, the first light-emitting unit includes a Ga-face n-type semiconductor layer, a Ga-face light-emitting layer, a Ga-face electron blocking layer, and a Ga-face p-type semiconductor layer sequentially stacked on the nucleation layer, the second light-emitting unit includes an N-face group III nitride material, the second light-emitting unit includes an N-face n-type semiconductor layer, an N-face light-emitting layer, an N-face electron blocking layer, and an N-face p-type semiconductor layer sequentially stacked on the second region, the Ga-face n-type semiconductor layer and the N-face n-type semiconductor layer, the Ga-face light-emitting layer and the N-face light-emitting layer, the Ga-face electron blocking layer and the N-face electron blocking layer, the Ga-face p-type semiconductor layer and the N-face p-type semiconductor layer are integrally formed, the Ga-face light-emitting layer and the N-face light-emitting layer are in the same plane, and the In component content in the Ga-face light-emitting layer is less than the In component content in the N-face light-emitting layer.

2. The epitaxial wafer of the LED device according to claim 1, characterized in that: The epitaxial wafer further includes a buffer layer, the buffer layer including an integrally formed Ga-face buffer layer and an N-face buffer layer, the Ga-face buffer layer being disposed between the nucleation layer and the first light-emitting unit, and the N-face buffer layer being disposed between the second region and the second light-emitting unit.

3. The epitaxial wafer of the LED device according to claim 2, characterized in that: The top surfaces of the Ga-face buffer layer and the N-face buffer layer facing away from the substrate are flush.

4. The epitaxial wafer of the LED device according to any one of claims 1 to 3, characterized in that: The substrate includes a sapphire substrate or a silicon carbide substrate.

5. The epitaxial wafer of the LED device according to claim 4, characterized in that: The sapphire substrate is a sapphire substrate with a bevel angle, the bevel angle direction of the sapphire substrate is c-plane offset from the m-axis, and the bevel angle is 1 to 4°.

6. The epitaxial wafer of the LED device according to claim 1, characterized in that: The material of the nucleation layer includes group III nitride.

7. The epitaxial wafer of the LED device according to claim 6, characterized in that: The nucleation layer includes an AlN nucleation layer or a GaN nucleation layer.

8. A method for preparing an epitaxial wafer of an LED device, characterized in that, Comprising: Providing a substrate, the surface of the substrate having a first region and a second region adjacent to the first region; Forming a nucleation layer in the first region; Meanwhile, an epitaxial structure layer is formed on the surface of the nucleation layer and the second region of the substrate surface. The epitaxial structure layer includes a first light-emitting unit and a second light-emitting unit. The first light-emitting unit is disposed on the nucleation layer, and the second light-emitting unit is disposed on the second region. Wherein, the first light-emitting unit includes a Ga-face group-III nitride material. The first light-emitting unit includes a Ga-face n-type semiconductor layer, a Ga-face light-emitting layer, a Ga-face electron blocking layer, and a Ga-face p-type semiconductor layer that are sequentially stacked on the nucleation layer. The second light-emitting unit includes an N-face group-III nitride material. The second light-emitting unit includes an N-face n-type semiconductor layer, an N-face light-emitting layer, an N-face electron blocking layer, and an N-face p-type semiconductor layer that are sequentially stacked on the second region. The Ga-face n-type semiconductor layer and the N-face n-type semiconductor layer, the Ga-face light-emitting layer and the N-face light-emitting layer, the Ga-face electron blocking layer and the N-face electron blocking layer, and the Ga-face p-type semiconductor layer and the N-face p-type semiconductor layer are integrally formed. The Ga-face light-emitting layer and the N-face light-emitting layer are in the same plane, and the In component content in the Ga-face light-emitting layer is less than the In component content in the N-face light-emitting layer.

9. The method for preparing an epitaxial wafer of an LED device according to claim 8, characterized in that, Specifically, it includes: Growing group-III nitride materials on the surface of the nucleation layer and the second region simultaneously. And during the growth process of the group-III nitride materials, adjusting the growth parameters of the group-III nitride materials so that the group-III nitride materials grown on the nucleation layer form Ga-face group-III nitride materials, while the group-III nitride materials grown on the second region form N-face group-III nitride materials. Wherein, the growth parameters include at least one of growth temperature, growth pressure, and V-III ratio of growth raw materials.

10. The method for preparing an epitaxial wafer of an LED device according to claim 9, wherein, Specifically, it includes: Growing the Ga-face n-type semiconductor layer and the N-face n-type semiconductor layer under a first preset condition. The first preset condition includes: the growth temperature is 1000~1100 °C, the growth pressure is 100~400 mbar, and the V-III ratio of growth raw materials is 500~2000. Growing the Ga-face light-emitting layer and the N-face light-emitting layer under a second preset condition. The second preset condition includes: the growth temperature is 700~900 °C, the growth pressure is 100~400 mbar, and the V-III ratio of growth raw materials is 10000~30000. Growing the Ga-face electron blocking layer and the N-face electron blocking layer under a third preset condition. The third preset condition includes: the growth temperature is 1000~1100 °C, the growth pressure is 100~200 mbar, and the V-III ratio of growth raw materials is 500~2000. Growing the Ga-face p-type semiconductor layer and the N-face p-type semiconductor layer under a fourth preset condition. The fourth preset condition includes: the growth temperature is 1000~1100 °C, the growth pressure is 100~400 mbar, and the V-III ratio of growth raw materials is 500~2000.

11. The method for preparing an epitaxial wafer of an LED device according to claim 8, characterized in that, It also includes: A buffer layer is formed on the surface of the nucleation layer and the second region, and a flat surface is formed at the top of the grown buffer layer; The epitaxial structure layer is grown on the buffer layer.

12. The method for preparing the epitaxial wafer of the LED device according to claim 11, wherein: The buffer layer includes a Ga-face buffer layer and an N-face buffer layer, and the preparation method specifically includes: The Ga-face buffer layer and the N-face buffer layer are grown simultaneously under a fifth preset condition, so that the top surfaces of the grown Ga-face buffer layer and the N-face buffer layer are flush. The fifth preset condition includes: the growth temperature is 1050-1150 °C, the growth pressure is 100-400 mbar, and the V-III ratio of the growth raw material is 100-1000.

13. The method for preparing an epitaxial wafer of an LED device according to claim 8, characterized in that, The step of forming the nucleation layer in the first region includes: Forming a nucleation layer on the surface of the substrate, removing the nucleation layer covering the second region to expose the second region; or Laying a mask on the second region; forming a nucleation layer in the first region; removing the mask to expose the second region.

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