Light-emitting diode epitaxial wafer and preparation method thereof

Abstract

The application provides a light emitting diode epitaxial wafer and a preparation method thereof. The light emitting diode epitaxial wafer comprises a composite electron blocking layer, the composite electron blocking layer is a superlattice structure, and the composite electron blocking layer comprises M first sublayers and second sublayers which are alternately stacked periodically; the first sublayer is a p-type doped Er a Al b Ga 1‑a‑b N layer, and the second sublayer is a p-type doped GaN layer. By converting the existing p-type AlGaN / GaN superlattice electron blocking layer into a p-type doped Er a Al b Ga 1‑a‑b N layer and a p-type doped GaN layer which are alternately stacked periodically, lattice matching on a heterojunction interface can be realized, interface stress can be eliminated, Er a Al b Ga 1‑a‑b N potential barrier height can be prevented from being reduced, a good electron blocking capability can be maintained, and the photoelectric efficiency of an LED can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a light emitting diode epitaxial wafer and a preparation method thereof. BACKGROUND

[0002] Gallium nitride (GaN) semiconductor material has direct wide band gap, fast electron saturation drift speed, high thermal conductivity and other excellent characteristics. At present, GaN-based LED has important application value in solid-state lighting, ultraviolet sterilization and disinfection, new display field and other aspects.

[0003] At present, the GaN-based blue-green-violet LED always includes a substrate and a GaN or AlGaN buffer layer, a three-dimensional island growth layer, a two-dimensional merged growth layer, an n-type GaN current expansion layer, a multi-quantum well light emitting layer, an electron blocking layer and a p-type GaN current expansion layer and a p-type ohmic contact layer on the substrate. Among them, the p-type wide band gap AlGaN layer doped with Mg is usually used as the electron blocking layer on the multi-quantum well barrier structure of the GaN-based LED. Although this structure can effectively block the leakage of hot electrons to the p-type layer, the p-type AlGaN has a high acceptor activation energy, and the hole concentration is low, which is not conducive to maintaining the light efficiency of the LED under the condition of large current of the LED, thereby reducing the light emitting efficiency of the LED.

[0004] On this basis, a p-type AlGaN / GaN superlattice structure begins to be used as an electron blocking layer of the LED. Through the polarization electric field in the p-type AlGaN / GaN superlattice structure, the energy band of the GaN layer is bent, the activation energy of Mg is reduced, and a higher concentration of holes is generated in the GaN layer. However, the interface stress generated by the lattice mismatch between AlGaN and GaN reduces the barrier height of AlGaN, and weakens the electron blocking effect. Secondly, in order to make the energy band of the GaN layer bent enough to reduce the activation energy of Mg, the thickness of the AlGaN layer needs to be kept thick enough, which hinders the transport of holes in the vertical direction. SUMMARY

[0005] In view of the defects in the prior art, the present application aims to provide a light emitting diode epitaxial wafer and a preparation method thereof, and aims to solve the technical problem of low light emitting efficiency of the light emitting diode in the prior art.

[0006] In order to achieve the above-mentioned purpose, the present application provides a light emitting diode epitaxial wafer in one aspect: comprising a composite electron blocking layer, the composite electron blocking layer is a superlattice structure, the composite electron blocking layer comprises M first sublayers and second sublayers which are alternately stacked periodically; wherein the first sublayer is a p-type doped Er a Al b Ga 1-a-b N layer, and the second sublayer is a p-type doped GaN layer.

[0007] Compared with the prior art, the present invention has the following advantages: by converting the existing p-type AlGaN / GaN superlattice electron blocking layer into a periodically stacked p-type doped Er a Al b Ga 1-a-b N layer and p-type doped GaN layer, using GaN / Er a Al b Ga 1-a-b N superlattice structure, since erbium is a light rare earth element, the atomic radius of rare earth element erbium (Er) is larger than that of Al (the atomic coefficient of erbium is 68, and the atomic coefficient of Al is 13). When rare earth element erbium is doped into AlGaN material, lattice distortion will be generated in AlGaN material, thereby improving the piezoelectric properties of AlGaN material; at the same time, due to the low electronegativity of erbium, the proportion of ionic bonds in AlN is increased. These two points further enhance the p-type doping of Er. a Al b Ga 1-a-b The N layer has a high spontaneous polarization coefficient, so the electron blocking layer Er a Al b Ga 1-a-b In the N and GaN periodic superlattice structure, a very thin p-type doped Er a Al b Ga 1-a-b The N layer can generate a large spontaneous polarization electric field, which causes the energy band of the GaN layer to bend sufficiently, thereby reducing the activation energy of Mg and obtaining a high concentration of holes. a Al b Ga 1-a-b The thickness of the N layer is designed to be very thin, and holes can be effectively transported in the vertical direction through the tunneling mechanism, and the Er component a is 24.9% of Er a Al b Ga 1-a-b N and GaN can achieve lattice matching on the heterojunction interface (when the Er element doping concentration is 24.9%, Er a Al b Ga 1-a-b The lattice constant of N is a=3.189, which is the same as that of GaN. It can achieve in-plane lattice constant matching and strain-free material growth, thereby reducing the dislocation density in the active area of ​​the device, reducing dislocation scattering and leakage channels, and avoiding Er a Al b Ga 1-a-b The N barrier height is reduced, maintaining good electron blocking capability, effectively improving the photoelectric efficiency and reliability of the LED.

[0008] Furthermore, the value range of M is: 2≤M≤12.

[0009] Furthermore, the p-type doped Er a Al b Ga 1-a-b The thickness of the N layer is 1 to 5 nm.

[0010] Furthermore, the thickness of the p-type doped GaN layer is 2-10 nm.

[0011] Furthermore, in the p-type doped Er a Al b Ga 1-a-b In N layers, the following conditions are met: 0.1 <a<0.25,0<b<1,a+b≤1,a<b。

[0012] Furthermore, the p-type doped Er a Al b Ga 1-a-b The doping elements of the N layer and the p-type doped GaN layer are both Mg, and the doping concentration of Mg is 1×10 19 ~2×10 20 cm -2 .

[0013] Furthermore, the light-emitting diode epitaxial wafer also includes: a substrate, and a buffer layer, a three-dimensional island growth layer, a two-dimensional merged growth layer, an n-type GaN current spreading layer, a multi-quantum well light-emitting layer, the composite electron blocking layer, a p-type GaN current spreading layer, and a p-type ohmic contact layer stacked in sequence on the substrate.

[0014] Another aspect of the present invention provides a method for preparing a light-emitting diode epitaxial wafer, which is used to prepare the above-mentioned light-emitting diode epitaxial wafer. The method for preparing the light-emitting diode epitaxial wafer comprises the following steps:

[0015] In the step of depositing the composite electron blocking layer, M periods of alternately stacked first sublayers and second sublayers are alternately grown to form a composite electron blocking layer with a superlattice structure;

[0016] Among them, the first sublayer is p-type doped Er a Al b Ga 1-a-b N layer, and the second sublayer is a p-type doped GaN layer.

[0017] Furthermore, the method further comprises the following steps:

[0018] Providing a substrate required for growth, and depositing a buffer layer on the substrate;

[0019] depositing a three-dimensional island growth layer on the buffer layer;

[0020] depositing a two-dimensional coalescence growth layer on the three-dimensional island growth layer;

[0021] depositing an n-type GaN current spreading layer on the two-dimensional coalescence growth layer;

[0022] depositing a multi-quantum well light emitting layer on the n-type GaN current spreading layer;

[0023] depositing a p-type layer on the multi-quantum well light emitting layer;

[0024] wherein the p-type layer comprises the composite electron blocking layer, the p-type GaN current spreading layer and the p-type ohmic contact layer deposited in sequence.

[0025] Further, the step of forming the composite electron blocking layer comprises:

[0026] introducing NH3 as the N source at a flow rate of 40-90 slm;

[0027] introducing TEGa as the Ga source at a flow rate of 600-1100 sccm;

[0028] introducing TMIn as the In source at a flow rate of 1000-2500 sccm;

[0029] introducing SiH4 as the n-type dopant at a flow rate of 100-300 sccm;

[0030] introducing TRIPEr as the Er source at a flow rate of 50-500 sccm;

[0031] introducing TMAl as the Al source at a flow rate of 10-300 sccm.

[0032] The details of one or more embodiments of the application are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the application will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a structural schematic diagram of a light emitting diode epitaxial wafer in the first embodiment of the application;

[0034] Figure 2 is a flow chart of a preparation method of a light emitting diode epitaxial wafer in the second embodiment of the application;

[0035] Explanation of main element symbols:

[0036] Substrate 10, buffer layer 20, three-dimensional island growth layer 30, two-dimensional coalescence growth layer 40, n-type GaN current spreading layer 50, multi-quantum well light emitting layer 60, p-type layer 70, composite electron blocking layer 710, p-type doped Er a Al b Ga1-a-b N layer 711 , p-type doped GaN layer 712 , p-type GaN current spreading layer 720 , and p-type ohmic contact layer 730 .

[0037] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0038] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0039] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0041] See also Figure 1The preparation of the wafer in the first embodiment of the application includes two steps of the preparation of the substrate 10 and the epitaxy process. The substrate 10 is a wafer made of semiconductor single crystal material, which can be directly used to produce semiconductor devices or be processed to form an epitaxial structure. Epitaxy refers to the process of growing a new single crystal on the substrate 10 which has been carefully processed by cutting, grinding, and polishing. The new single crystal can be the same material as the substrate 10 or a different material (i.e. homoepitaxy or heteroepitaxy). The new single crystal is grown in the same crystal phase as the substrate 10, which is called epitaxial structure. The device is fabricated on the epitaxial structure in a positive epitaxy, or on the substrate 10 in a negative epitaxy. The LED epitaxial structure includes the substrate 10, the buffer layer 20, the three-dimensional island growth layer 30, the two-dimensional merged growth layer 40, the n-type GaN current spreading layer 50, the multi-quantum well light emitting layer 60, and the p-type layer 70. The buffer layer 20, the three-dimensional island growth layer 30, the two-dimensional merged growth layer 40, the n-type GaN current spreading layer 50, the multi-quantum well light emitting layer 60, and the p-type layer 70 are sequentially stacked on the substrate 10 from bottom to top. The p-type layer 70 includes the recombination electron blocking layer 710, the p-type GaN current spreading layer 720, and the p-type ohmic contact layer 730, which are sequentially stacked on the multi-quantum well light emitting layer 60 from bottom to top. Preferably, the LED epitaxial structure is grown by using a metal organic chemical vapor deposition (MOCVD) device.

[0042] In the embodiment, the recombination electron blocking layer 710 includes the first sub-layer and the second sub-layer arranged alternately. Preferably, the first sub-layer is p-type doped Er a Al b Ga 1-a-bN layer 711, the second sub-layer is a p-type doped GaN layer 712. Because the effective mass of electrons is smaller than that of holes, under high current working conditions, the LED will have electron overflow, and the electrons will quickly cross the multi-quantum well light emitting layer 60 to reach the p-type layer 70, resulting in non-radiative recombination. In the industry, a p-type wide bandgap AlGaN layer doped with Mg or a p-type AlGaN / GaN superlattice structure optimized on this basis is often used as an electron blocking layer on the multi-quantum well barrier structure to avoid the phenomenon of electron overflow. Although these two structures can effectively block the leakage of hot electrons to the p-type layer, the p-type AlGaN layer has a relatively high acceptor activation energy, which results in a low hole concentration. In the p-type AlGaN / GaN superlattice structure, the polarization electric field causes the energy band of the GaN layer to bend, reducing the activation energy of Mg, thereby generating a higher concentration of holes in the GaN layer. However, the lattice mismatch between AlGaN and GaN increases the interfacial compressive and tensile stress, resulting in a rough interface and a relatively high dislocation density. As the interfacial compressive and tensile stress increases, the AlGaN barrier height decreases, affecting the electron blocking. The reduced AlGaN barrier height weakens the electron blocking effect. Secondly, in order to make the energy band of the GaN layer bend enough to reduce the activation energy of Mg, the thickness of the AlGaN layer needs to be thick enough. However, the effective mass of holes is large and their mobility is low, which hinders the vertical transport of holes. By replacing the traditional AlGaN layer with the composite electron blocking layer 710, the Er component a is 24.9%, and the p-type doped Er a Al b Ga 1-a-b N layer 711 and the p-type doped GaN layer 712 can achieve lattice matching at the heterojunction interface, with an interfacial stress of essentially 0, a smooth interface surface, and a relatively small dislocation density. This eliminates interfacial stress and avoids the Er a Al b Ga 1-a-b N barrier height from decreasing, maintaining good electron blocking ability and effectively improving the photoelectric efficiency of the LED. Secondly, the p-type doped Er a Al b Ga 1-a-b N layer 711 has a larger bandgap than the AlGaN layer, and even if the thickness is very thin, it can have a high enough barrier height to block electrons. The p-type doped Er a Al b Ga 1-a-b N layer 711 can be designed to be much thinner than the AlGaN layer, and still have the ability to block electrons. The relatively thin p-type doped Er a Al b Ga 1-a-bThe N layer 711 can further improve the transport ability of holes in the vertical direction, thereby improving the radiative recombination efficiency of electrons and holes.

[0043] By converting the existing p-type AlGaN / GaN superlattice electron blocking layer into a periodically stacked p-type doped Er a Al b Ga 1-a-b N layer 711 and the p-type doped GaN layer 712, i.e., a GaN / Er a Al b Ga 1-a-b N superlattice structure, since the atomic radius of the rare earth element Er is larger than that of Al, the incorporation of Er into AlGaN will cause lattice distortion in the AlGaN material, thereby improving the piezoelectric properties of AlGaN; at the same time, since the electronegativity of Er is small, the proportion of ionic bonds in AlN is increased, which further enhances the high spontaneous polarization coefficient of the p-type doped Er a Al b Ga 1-a-b N layer 711, therefore, the p-type doped Er a Al b Ga 1-a-b N layer 711 and the p-type doped GaN layer 712 in the periodic superlattice structure, a very thin p-type doped Er a Al b Ga 1-a-b N layer 711 can generate a large spontaneous polarization electric field to sufficiently bend the energy band of the p-type doped GaN layer 712, thereby reducing the activation energy of Mg, obtaining high-concentration holes, and further improving the radiative recombination efficiency of electrons and holes, and reducing the efficiency droop phenomenon.

[0044] The composite electron blocking layer 710 includes the p-type doped Er a Al b Ga 1-a-b N layer 711 and the p-type doped GaN layer 712, the p-type doped Er a Al b Ga 1-a-b N layer 711 and the p-type doped GaN layer 712 are stacked with each other to form a periodic structure, and the composite electron blocking layer 710 includes M periodic structures, wherein the value of M is in the range of 2≤N≤12. By alternately growing the p-type doped Er a Al b Ga 1-a-b N layer 711 and the p-type doped GaN layer 712, the p-type doped Er a Alb Ga 1-a-b N layer 711 and the relatively thick p-type doped GaN layer 712 are alternately grown, sufficient barrier height can be ensured to have good blocking ability for electrons, and the transport ability of holes in the vertical direction can be further improved. The p-type doped Er a Al b Ga 1-a-b The thickness of the N layer 711 is 1-5 nanometers, and the thickness of the p-type doped GaN layer 712 is 2-10 nanometers. By controlling the period M in the value range, the total thickness of the composite electron blocking layer 710 can be controlled to be about 10-100 nanometers, so as to avoid that the thickness of the composite electron blocking layer 710 is too thick and affects the light-emitting efficiency of the p surface of the vertical chip.

[0045] In the embodiment, the doping elements of the first sub-layer and the second sub-layer are both Mg, that is, the p-type doped Er a Al b Ga 1-a-b The doping elements of the N layer 711 and the p-type doped GaN layer 712 are both Mg, Mg is a divalent element, and Ga in the p-type doped GaN layer 712 is a trivalent element. At this time, when Mg atoms replace Ga atoms, one electron is less, which is equivalent to one more hole. When the Er component a is 24.9%, the p-type doped Er a Al b Ga 1-a-b The N layer 711 and the p-type doped GaN layer 712 can realize lattice matching on the heterojunction interface. The interface stress is basically 0, the interface surface is smooth, the dislocation density is relatively small, the interface stress is eliminated, and Er a Al b Ga 1-a-b N barrier height is reduced, which can play a role in blocking electron transition, and the p-type doped Er a Al b Ga 1-a-b In the periodic superlattice structure of the N layer 711 and the p-type doped GaN layer 712, the very thin p-type doped Er a Al b Ga 1-a-b The N layer 711 can generate a large spontaneous polarization electric field to make the energy band of the p-type doped GaN layer 712 sufficiently curved, thereby reducing the activation energy of Mg and obtaining high-concentration holes, and the relatively thin p-type doped Er a Al b Ga 1-a-bThe N layer 711 further enhances the transport capacity of holes in the vertical direction, allowing more electrons and holes to be confined in the multi-quantum well light-emitting layer 60, where electrons and holes recombine to emit light. However, Mg is doped in both the first and second sub-layers, forming an artificial gap in crystallography. Although Mg doping replaces Ga to provide holes, overdoping can also cause excessive gaps in the GaN layer, forming dislocations. In some preferred implementations of this embodiment, the Mg doping concentration of the composite electron blocking layer 710 is 1×10 20 cm -2 It can be understood that, along the stacking direction away from the LED epitaxial structure, the Mg doping concentration in the plurality of composite electron blocking layers 710 decreases layer by layer or remains unchanged.

[0046] The first sublayer is p-type doped Er a Al b Ga 1-a-b N layer 711, namely the ErAlGaN layer is p-type doped Er a Al b Ga 1-a-b N layer 711, the p-type doped Er a Al b Ga 1-a-b In the N layer 711, the Er component is a, the Al component is b, and the Ga component is 1-ab. In some preferred implementations of this embodiment, the Er component a is 0.249, the Al component b is 0.351, and the Ga component 1-ab is 0.4. a Al b Ga 1-a-b The Er composition in the N layer 711 is different, and the lattice matching between it and the p-type doped GaN layer 712 will also change accordingly. By controlling the Er composition within a value range, the p-type doped Er can be made a Al b Ga 1-a-b The interface compressive tensile stress between the N layer 711 and the p-type doped GaN layer 712 is reduced. Preferably, when a is 0.249, the p-type doped Er a Al b Ga 1-a-b There is no interfacial compressive stress between the N layer 711 and the p-type doped GaN layer 712, which avoids Er a Al b Ga 1-a-b The N-layer barrier height decreases, maintaining good electron blocking ability.

[0047] In another aspect, the second embodiment of the present application also provides a method for preparing the LED epitaxial structure, for preparing the LED epitaxial structure in the above technical solution, please refer to Figure 2 The LED epitaxial structure is grown by using a metal organic chemical vapor deposition (MOCVD) device, in which high-purity ammonia (NH3) is used as a N (nitrogen) source, trimethyl gallium (TMGa) and triethyl gallium (TEGa) are used as Ga (gallium) sources, trimethyl indium (TMIn) is used as an In (indium) source, and trimethyl aluminum (TMAl) is used as an Al (aluminum) source, in which silane (SiH4) is used as an n-type dopant, and bis-cyclopentadienyl magnesium (CP2Mg) is used as a p-type dopant, and high-purity H2 (hydrogen) or N2 (nitrogen) or a mixture of high-purity H2 (hydrogen) and N2 (nitrogen) is used as a carrier gas, and specifically, the method comprises the following steps:

[0048] S10: providing a substrate required for growth, and depositing a buffer layer on the substrate;

[0049] In this step, an AlN buffer layer or a GaN buffer layer or an AlGaN buffer layer is deposited on the substrate by using a metal organic vapor chemical deposition method, the growth pressure of the reaction chamber is controlled to be 50-200 torr, the rotation speed of the graphite base is controlled to be 500-1000 r / min, NH3 with a flow rate of 20 slm-70 slm is introduced as a N (nitrogen) source, TMGa with a flow rate of 20-150 sccm is introduced as a Ga (gallium) source, and TMAl (trimethyl aluminum) with a flow rate of 20-120 sccm is introduced as an aluminum source, so as to deposit the AlN buffer layer or the GaN buffer layer or the AlGaN buffer layer with a thickness of 5 nm-15 nm on the substrate.

[0050] S20: depositing a three-dimensional island growth layer on the buffer layer;

[0051] In this step, NH3 with a flow rate of 10 slm-60 slm is introduced as a N (nitrogen) source, TMGa with a flow rate of 200 sccm-500 sccm is introduced as a Ga (gallium) source, the temperature of the reaction chamber is increased to 1060°C-1090°C, the pressure is controlled to be 200 torr-500 torr, and the rotation speed of the graphite base is reduced to 500-1000 r / min, so as to grow a GaN three-dimensional island growth layer, and the thickness of the three-dimensional island growth layer is controlled to be 500 nm-1000 nm.

[0052] S30: depositing a two-dimensional merged growth layer on the three-dimensional island growth layer;

[0053] In this step, the temperature of the reaction chamber is increased to 1100-1450℃, the pressure is controlled to 150-250 torr, the rotation speed of the graphite susceptor is controlled to 800-1200 r / min, NH3 is introduced as the N source at a flow rate of 40-90 slm, TMGa is introduced as the Ga source at a flow rate of 300-1000 sccm, and a GaN two-dimensional coalescence growth layer is grown, with the thickness of the two-dimensional coalescence growth layer controlled to 1000-2000 nm.

[0054] S40: depositing an n-type GaN current spreading layer on the two-dimensional coalescence growth layer;

[0055] In this step, the temperature of the reaction chamber is decreased to 1090-1100℃, the pressure is controlled to 150-250 torr, the rotation speed of the graphite susceptor is controlled to 800-1200 r / min, NH3 is introduced as the N source at a flow rate of 30-80 slm, TMGa is introduced as the Ga source at a flow rate of 200-500 sccm, and SiH4 is introduced as the n-type dopant at a flow rate of 100-300 sccm, with the doping concentration of Si controlled to 8E18 atoms / cm 3 -1.5E19 atoms / cm 3 , and the n-type GaN current spreading layer is grown, with the thickness of the n-type GaN layer controlled to 1500-2000 nm.

[0056] Specifically, the n-type GaN current spreading layer serves as the main epitaxial layer for providing electrons, and when the n-type GaN layer is grown, SiH4 is introduced to provide Si elements. Si is a tetravalent element, while Ga in the n-type GaN layer is a trivalent element. At this time, when Si atoms replace Ga atoms, electrons are provided, thereby forming the n-type GaN layer for providing electrons.

[0057] S50: depositing a multiple quantum well light-emitting layer on the n-type GaN current spreading layer;

[0058] Specifically, in this step, N multiple quantum well light-emitting layers are deposited on the n-type GaN current spreading layer by alternating growth, the temperature of the reaction chamber is decreased to 780-900℃, the pressure is controlled to 200-250 torr, the rotation speed of the graphite susceptor is controlled to 500-1600 r / min, and InGaN quantum well layers and GaN quantum barrier layers are alternately stacked, with the growth temperature of the InGaN quantum well layers controlled to 780-810℃, the growth temperature of the GaN quantum barrier layers controlled to 860-900℃, and the growth thickness controlled to 12-16 nm, where 5≤N≤9, and N is a positive integer.

[0059] S60: depositing a p-type layer on the multi-quantum well light emitting layer.

[0060] In this step, the p-type layer includes a composite electron blocking layer, a p-type GaN current spreading layer and a p-type ohmic contact layer which are stacked, the temperature of the reaction chamber is raised to 850-950°C, the pressure is controlled to be 150-250 torr, the rotation speed of the graphite disc carrying the substrate is controlled to be 800-1200 r / min, NH3 with a flow rate of 40-90 slm is introduced as the N source, TMGa with a flow rate of 600-1100 sccm is introduced as the Ga source, TMAl with a flow rate of 10-300 sccm is introduced as the Al source, TRIPEr with a flow rate of 50-500 sccm is introduced as the Er source, and CP2Mg is introduced as the dopant, wherein the doping concentration of Mg is 1.5E20 atoms / cm 3 The composite electron blocking layer is grown on the multi-quantum well light emitting layer, and the thickness of the composite electron blocking layer is controlled to be 20 nm.

[0061] Specifically, when the composite electron blocking layer is deposited, M periods of the p-type doped Er a Al b Ga 1-a-b N layer and the p-type doped GaN layer are alternately grown.

[0062] The Er a Al b Ga 1-a-b N / GaN superlattice structure is used, which improves the potential barrier height for electrons in the multi-quantum well light emitting layer and reduces the leakage of electrons. Since the p-type doped Er a Al b Ga 1-a-b N layer and the p-type doped GaN layer can realize in-plane lattice constant matching and strain-free material growth, preferably, when the component of Er in the p-type doped Er a Al b Ga 1-a-b N layer is 24.9%, ErAlN has the same lattice constant as GaN, thereby reducing the dislocation density in the active region of the device, reducing dislocation scattering and leakage channels, and the device will have superior performance and reliability.

[0063] The temperature of the reaction chamber is raised to 850-970 DEG C, the pressure is controlled to 150-250 torr, the rotating speed of the graphite disc is controlled to 800-1200 r / min, NH3 with a flow rate of 40-90 slm is used as the N source, TMGa with a flow rate of 600-1100 sccm is used as the Ga source, and dimethyl magnesium (CP2Mg) is used as the dopant, wherein the doping concentration of Mg is 1E19-5.5E20 atoms / cm 3 The p-type GaN current spreading layer is grown and the thickness is controlled to be 20 nm, and the p-type contact layer is grown and the thickness is controlled to be 5 nm.

[0064] The third embodiment of the present application provides a light emitting diode epitaxial wafer, wherein the light emitting diode epitaxial wafer in the third embodiment is different from the light emitting diode epitaxial wafer in the first embodiment in that:

[0065] The p-type doped Er a Al b Ga 1-a-b In the N layer, the component a of Er is 0.1, the component b of Al is 0.42, and the component 1-a-b of Ga is 0.48.

[0066] The fourth embodiment of the present application also provides a light emitting diode epitaxial wafer, wherein the light emitting diode epitaxial wafer in the fourth embodiment is different from the light emitting diode epitaxial wafer in the first embodiment in that:

[0067] The p-type doped Er a Al b Ga 1-a-b In the N layer, the component a of Er is 0.2, the component b of Al is 0.52, and the component 1-a-b of Ga is 0.28.

[0068] The fifth embodiment of the present application also provides a light emitting diode epitaxial wafer, wherein the light emitting diode epitaxial wafer in the fifth embodiment is different from the light emitting diode epitaxial wafer in the first embodiment in that:

[0069] The doping concentration of Mg in the first sub-layer and the second sub-layer is 0.

[0070] Comparative Example One

[0071] The light emitting diode epitaxial wafer in the sixth embodiment is different from the light emitting diode epitaxial wafer in the first embodiment in that:

[0072] The p-type doped Er a Al b Ga 1-a-b In the N layer, the component a of Er is 0, that is, the first sub-layer is a p-type doped AlGaN layer.

[0073] Comparative Example 2

[0074] A light emitting diode epitaxial wafer, the light emitting diode epitaxial wafer in the embodiment is different from the light emitting diode epitaxial wafer in the first embodiment in that:

[0075] p-type doped Er a Al b Ga 1-a-b The component a of Er in the N layer is 0, that is, the first sublayer is a p-type doped AlGaN layer.

[0076] And the doping concentration of Mg in the first sublayer and the second sublayer is 0.

[0077] The light emitting diode epitaxial wafers prepared in each of the above-mentioned embodiments 1, 3-5 and comparative examples 1-2 are prepared into chips of about 457.5 nm waveband and 10x24 mil size, a current of 20 mA is passed, and photoelectric tests are performed, and the corresponding preparation parameters and test results are shown in the following table:

[0078]

[0079] In actual application, the light emitting diode epitaxial wafer structures in the above-mentioned embodiments 1-4 and comparative examples 1-2 of the present application are respectively adopted, and the light emitting diode epitaxial wafers prepared in each example are prepared into chips of about 457.5 nm waveband and 10x24 mil size, a current of 20 mA is passed, and photoelectric tests are performed, and the test data is shown in the above table. It should be noted that, in order to ensure the reliability of the verification results, when the epitaxial structures corresponding to the above-mentioned embodiments 1-4 and comparative examples 1-2 of the present application are prepared, in addition to the above-mentioned parameters being different, other processes and parameters should be kept consistent.

[0080] From the above table, it can be seen that the voltage of the epitaxial wafer prepared by the growth method provided in the embodiment 1 of the present application is reduced by 0.08 V compared with comparative example 1, the brightness is increased by 3.9%, the voltage is reduced by 0.39 V compared with comparative example 2, and the brightness is increased by 1.37%. The voltage of the epitaxial wafer prepared by the growth method provided in the embodiment 2 of the present application is reduced by 0.03 V compared with comparative example 1, the brightness is increased by 1.43%, the voltage is reduced by 0.34 V compared with comparative example 2, and the brightness is increased by 1.21%. The voltage of the epitaxial wafer prepared by the growth method provided in the embodiment 3 of the present application is reduced by 0.05 V compared with comparative example 1, the brightness is increased by 2.41%, the voltage is reduced by 0.36 V compared with comparative example 2, and the brightness is increased by 2.19%. The voltage of the epitaxial wafer prepared by the growth method provided in the embodiment 4 of the present application is reduced by 0.02 V compared with comparative example 1, the brightness is increased by 3.1%, the voltage is reduced by 0.33 V compared with comparative example 2, and the brightness is increased by 2.97%.

[0081] In summary, by transforming the existing p-type AlGaN / GaN superlattice electron blocking layer into a periodically stacked p-type doped Er a Al b Ga 1-a-b N layer and p-type doped GaN layer, using GaN / Er a Al b Ga 1-a-b N superlattice structure, since erbium is a light rare earth element, the atomic radius of rare earth element erbium (Er) is larger than that of Al (the atomic coefficient of erbium is 68, and the atomic coefficient of Al is 13). When rare earth element erbium is doped into AlGaN material, lattice distortion will be generated in AlGaN material, thereby improving the piezoelectric properties of AlGaN material; at the same time, due to the low electronegativity of erbium, the proportion of ionic bonds in AlN is increased. These two points further enhance the p-type doping of Er. a Al b Ga 1-a-b The N layer has a high spontaneous polarization coefficient, so the electron blocking layer Er a Al b Ga 1-a-b In the N and GaN periodic superlattice structure, a very thin p-type doped Er a Al b Ga 1-a-b The N layer can generate a large spontaneous polarization electric field, which causes the energy band of the GaN layer to bend sufficiently, thereby reducing the activation energy of Mg and obtaining a high concentration of holes. a Al b Ga 1-a-b The thickness of the N layer is designed to be very thin, and holes can be effectively transported in the vertical direction through the tunneling mechanism, and the Er component a is 24.9% of Er a Al b Ga 1-a-b N and GaN can achieve lattice matching on the heterojunction interface (when the Er element doping concentration is 24.9%, Er a Al b Ga 1-a-b The lattice constant of N is a=3.189, which is the same as that of GaN. It can achieve in-plane lattice constant matching and strain-free material growth, thereby reducing the dislocation density in the active area of ​​the device, reducing dislocation scattering and leakage channels, and avoiding Er a Al b Ga 1-a-b The N barrier height is reduced, maintaining good electron blocking ability, effectively improving the photoelectric efficiency and reliability of LEDs;

[0082] The doping elements of the first sub-layer and the second sub-layer are both Mg, that is, the p-type doped Er a Al b Ga1-a-b The doping elements of the N layer 711 and the p-type doped GaN layer 712 are both Mg, which is a divalent element, and Ga in the p-type doped GaN layer 712 is a trivalent element. At this time, when the Mg atom replaces the Ga atom, one less electron is equivalent to one more hole. When the Er component a is 24.9%, the p-type doped Er a Al b Ga 1-a-b The N layer 711 and the p-type doped GaN layer 712 can achieve lattice matching on the heterojunction interface. The interface stress of the lattice matching is basically 0, the interface surface is smooth, the dislocation density is relatively small, and the interface stress is eliminated to avoid Er a Al b Ga 1-a-b The height of the N barrier decreases, which can block the electron transition, and the p-type doped Er a Al b Ga 1-a-b In the periodic superlattice structure of the N layer 711 and the p-type doped GaN layer 712, a very thin p-type doped Er a Al b Ga 1-a-b The N layer 711 can generate a large spontaneous polarization electric field to cause the energy band of the p-type doped GaN layer 712 to be sufficiently bent, thereby reducing the activation energy of Mg and obtaining a high concentration of holes. a Al b Ga 1-a-b The N layer 711 further enhances the transport capability of holes in the vertical direction, allowing more electrons and holes to be confined in the multi-quantum well light-emitting layer 60. Electrons and holes recombine and emit light in the multi-quantum well light-emitting layer 60, further enhancing the luminescence efficiency of the device.

[0083] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0084] The above-described embodiments merely illustrate several embodiments of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A light-emitting diode epitaxial wafer comprising a composite electron blocking layer, characterized in that: The composite electron blocking layer is a superlattice structure, and the composite electron blocking layer includes M periods of alternately stacked first sublayers and second sublayers; Among them, the first sublayer is p-type doped Er a Al b Ga 1-a-b N layer, the second sublayer is a p-type doped GaN layer; The value range of M is: 2≤M≤12; The p-type doped Er a Al b Ga 1-a-b The thickness of the N layer is 1 to 5 nm; The thickness of the p-type doped GaN layer is 2 to 10 nm; In the p-type doped Er a Al b Ga 1-a-b In N layers, the following conditions are met: 0.1 <a<0.25,0<b<1,a+b≤1,a<b。 2. The light emitting diode epitaxial wafer according to claim 1, characterized in that: The p-type doped Er a Al b Ga 1-a-b The doping elements of the N layer and the p-type doped GaN layer are both Mg, and the doping concentration of Mg is 1×10 19 ~2×10 20 cm -2 .

3. The light emitting diode epitaxial wafer according to any one of claims 1 to 2, characterized in that: The light-emitting diode epitaxial wafer further includes: a substrate, and a buffer layer, a three-dimensional island growth layer, a two-dimensional merged growth layer, an n-type GaN current spreading layer, a multi-quantum well light-emitting layer, the composite electron blocking layer, a p-type GaN current spreading layer, and a p-type ohmic contact layer stacked in sequence on the substrate.

4. A method for preparing a light-emitting diode epitaxial wafer, for preparing the light-emitting diode epitaxial wafer according to any one of claims 1 to 3, characterized in that: The method for preparing the light emitting diode epitaxial wafer comprises the following steps: In the step of depositing the composite electron blocking layer, M periods of alternately stacked first sublayers and second sublayers are alternately grown to form a composite electron blocking layer with a superlattice structure; Among them, the first sublayer is p-type doped Er a Al b Ga 1-a-b N layer, and the second sublayer is a p-type doped GaN layer.

5. The preparation method according to claim 4, characterized in that The following steps are also included: Providing a substrate required for growth, and depositing a buffer layer on the substrate; depositing a three-dimensional island growth layer on the buffer layer; depositing a two-dimensional merged growth layer on the three-dimensional island growth layer; depositing an n-type GaN current spreading layer on the two-dimensional merged growth layer; depositing a multi-quantum well light-emitting layer on the n-type GaN current spreading layer; depositing a p-type layer on the multi-quantum well light-emitting layer; The p-type layer includes the composite electron blocking layer, the p-type GaN current spreading layer, and the p-type ohmic contact layer which are deposited in sequence.

6. The preparation method according to claim 4, characterized in that The step of forming a composite electron blocking layer of a superlattice structure comprises: NH3 was introduced as a N source at a flow rate of 40–90 slm; TEGa with a flow rate of 600-1100 sccm was introduced as a Ga source; TMIn with a flow rate of 1000~2500sccm was introduced as the In source; SiH4 was introduced as an n-type dopant at a flow rate of 100-300 sccm; TRIPer was introduced as Er source at a flow rate of 50-500 sccm; TMAl with a flow rate of 10~300 sccm was introduced as the Al source.

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