WO2019015217A1 - 一种深紫外led - Google Patents

一种深紫外led Download PDF

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WO2019015217A1
WO2019015217A1 PCT/CN2017/114551 CN2017114551W WO2019015217A1 WO 2019015217 A1 WO2019015217 A1 WO 2019015217A1 CN 2017114551 W CN2017114551 W CN 2017114551W WO 2019015217 A1 WO2019015217 A1 WO 2019015217A1
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layer
type
type algan
substrate
composition
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何苗
黄波
王成民
王润
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广东工业大学
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/04—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction
    • H01L33/06—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a quantum effect structure or superlattice, e.g. tunnel junction within the light emitting region, e.g. quantum confinement structure or tunnel barrier
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/14—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure
    • H01L33/145—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies with a carrier transport control structure, e.g. highly-doped semiconductor layer or current-blocking structure with a current-blocking structure
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen

Definitions

  • UV LED based on AlGaN (aluminum gallium nitride) material is the main trend of the development of nitride technology and the development of third-generation material technology, and has broad application prospects. UV LEDs are used in a wide range of applications such as air and water purification, disinfection, UV medical, high density optical storage systems, full color displays, and solid white light illumination. As a major industry after semiconductor lighting, semiconductor ultraviolet light source has attracted widespread attention in the semiconductor optoelectronic industry.
  • UV LEDs are currently in the technological development stage, and there are still some problems that are difficult to break through. For example, the internal quantum efficiency and emission power of AlGaN-based UV LEDs are relatively low.
  • the present invention provides a deep ultraviolet LED to solve the problem of low internal quantum efficiency and low transmission power of the deep ultraviolet LED in the prior art.
  • the present invention provides the following technical solutions:
  • a deep ultraviolet LED that includes:
  • An N-type AlGaN layer located on the surface of the undoped buffer layer facing away from the substrate;
  • a multiple quantum well structure located on the surface of the N-type AlGaN layer facing away from the substrate;
  • the V-type Al composition graded P-type AlGaN structure adopts polarization doping, and wherein the Al composition in the V-type Al composition graded P-type AlGaN structure and the multi-quantum well structure Different Al components;
  • the V-type Al composition graded P-type AlGaN structure comprises at least one layer of Al 0.65 Ga 0.35 N and at least one layer of Al x Ga 1-x N, said Al 0.65 Ga 0.35 N layer and said The Al x Ga 1-x N layers are alternately stacked, wherein the Al 0.65 Ga 0.35 N layer is grown on the surface of the multiple quantum well structure.
  • the value of x in the Al x Ga 1-x N layer ranges from 0.3 ⁇ x ⁇ 0.4.
  • each of the V-type Al composition graded P-type AlGaN structures has a thickness of 12.22 nm and a total of 110 nm.
  • the V-type Al composition graded P-type AlGaN structure has a doping concentration of 5 ⁇ 10 17 cm -3 and a growth temperature of 990 ° C.
  • the substrate is a C-plane sapphire substrate.
  • the undoped buffer layer is an undoped Al 0.5 Ga 0.5 N buffer layer having a thickness of 1.5 ⁇ m, a growth temperature of 530 ° C, and the undoped Al 0.5 Ga 0.5 N buffer layer is Recrystallization at 1050 ° C for 6 minutes.
  • the N-type AlGaN layer is an Al 0.5 Ga 0.5 N layer having a thickness of 3.0 ⁇ m, a doping concentration of 5 ⁇ 10 18 cm ⁇ 3 , and a growth temperature of 1050° C.
  • the multiple quantum well structure is a stacked structure of 5 cycles of an Al 0.36 Ga 0.64 N layer and an Al 0.5 Ga 0.5 N layer, wherein the Al 0.36 Ga 0.64 N layer is grown on the N-type AlGaN layer. surface.
  • the growth temperature of the multiple quantum well structure is 1020 ° C, wherein the thickness of the Al 0.36 Ga 0.64 N layer per layer is 10 nm, and the thickness of the Al 0.5 Ga 0.5 N layer per layer is 3 nm.
  • the deep ultraviolet LED provided by the present invention has a V-type Al composition graded P-type AlGaN structure between the multiple quantum well structure and the P-type GaN layer.
  • the V-type Al composition graded P-type AlGaN structure adopts a polarization doping method, a higher concentration of holes can be obtained, thereby increasing the hole injection rate, so that more holes are injected into the active region.
  • the probability of recombination of electrons and holes in the active region is increased, thereby improving the internal quantum efficiency and the emission power of the ultraviolet LED.
  • the V-type Al composition graded P-type AlGaN structure and the last barrier layer of the multiple quantum well structure have different Al composition, and the active region has a higher electron concentration, so that the V-shaped Al group
  • the graded P-type AlGaN structure also functions as an electron blocking layer, which can more effectively block the leakage of electrons from the active region, thereby replacing the electron blocking layer (EBL), while the electron leakage is reduced, and the hole injection efficiency is increased.
  • EBL electron blocking layer
  • the probability of recombination of electrons and holes increases, further increasing the internal quantum efficiency and emission power of the ultraviolet LED.
  • the concentration of electrons and holes increases, and the recombination probability increases.
  • the efficiency of recombination of electrons and holes increases, and the polarization electric field formed when the internal electrons and holes are not recombined is weakened due to the compounding and compounding probability. That is, the deep ultraviolet LED provided by the invention can weaken the polarization electric field in the active region quantum well structure, weaken the quantum confinement Stark effect, thereby causing more electron and hole wave functions to overlap, and the active region radiation recombination greatly Increased, the internal quantum efficiency of the UV LED is improved.
  • FIG. 1 is a schematic structural diagram of a deep ultraviolet LED according to an embodiment of the present invention
  • FIG. 2 is a schematic diagram of a P-type AlGaN structure in which a V-type Al composition is graded in a deep ultraviolet LED according to an embodiment of the present invention.
  • the internal quantum efficiency and emission power of the prior art AlGaN-based ultraviolet LEDs are relatively low.
  • the reason for the low luminous efficiency of AlGaN-based deep ultraviolet LED light source is as follows: the low carrier efficiency of high Al composition AlGaN material limits the increase of quantum efficiency in ultraviolet LED; the structural properties of high Al composition AlGaN material determine its Light extraction efficiency is low.
  • a deep ultraviolet LED comprising:
  • An N-type AlGaN layer located on the surface of the undoped buffer layer facing away from the substrate;
  • a multiple quantum well structure located on the surface of the N-type AlGaN layer facing away from the substrate;
  • the V-type Al composition graded P-type AlGaN structure adopts polarization doping, and wherein the V The Al composition in the graded Al composition graded P-type AlGaN structure is different from the Al composition of the multiple quantum well structure;
  • a V-type Al composition graded P-type AlGaN structure is disposed between the multiple quantum well structure and the P-type GaN layer. Since the V-type Al composition graded P-type AlGaN structure adopts a polarization doping method, a higher concentration of holes can be obtained, thereby increasing the hole injection rate, so that more holes are injected into the quantum well of the active region. The probability of recombination of electrons and hole radiation in the active region is improved, thereby improving the internal quantum efficiency and the transmission power of the ultraviolet LED.
  • the V-type Al component The graded P-type AlGaN structure also functions as an electron blocking layer, which can more effectively block the leakage of electrons from the active region, and further improve the internal quantum efficiency and the emission power of the ultraviolet LED.
  • the P-type AlGaN structure with V-type Al composition grading due to the P-type AlGaN structure with V-type Al composition grading, the polarization electric field in the quantum well structure of the active region can be weakened, and the quantum-confined Stark effect is weakened, thereby making more electrons and hole waves. The functions overlap, the radiative recombination in the active region is greatly increased, and the internal quantum efficiency of the ultraviolet LED is improved.
  • a deep ultraviolet LED according to an embodiment of the present invention, comprising: a substrate 1; an undoped buffer layer 2 on a surface of the substrate 1; and an undoped buffer layer 2 facing away from the substrate 1 a surface of the N-type AlGaN layer 3; a multi-quantum well structure 4 located on the surface of the N-type AlGaN layer 3 facing away from the substrate 1; a P-type AlGaN structure 5 having a V-type Al composition gradient away from the surface of the multi-quantum well structure 4,
  • the V-type Al composition graded P-type AlGaN structure 5 is doped with polarization, and wherein the Al composition in the V-type Al composition graded P-type AlGaN structure 5 is different from the Al composition of the multiple quantum well structure 4;
  • a P-type GaN layer 6 located away from the surface of the substrate 1 in a P-type AlGaN structure 5 in which the V-type Al composition is graded.
  • the specific structure of the P-type AlGaN structure in which the V-type Al composition is graded is not limited.
  • the V-type Al composition-graded P-type AlGaN structure 5 includes At least one layer of Al 0.65 Ga 0.35 N layer a and at least one layer of Al x Ga 1-x N layer b, Al 0.65 Ga 0.35 N layer a and Al x Ga 1-x N layer b are alternately stacked, wherein Al 0.65 Ga 0.35 The N layer a is in contact with the surface of the multiple quantum well structure. That is, the Al composition of the deep ultraviolet LED provided by the embodiment of the present invention is gradually changed from 0.65 at the boundary with the last barrier layer of the multiple quantum well.
  • the P-type AlGaN structure in which the V-type Al composition is graded in the embodiment of the present invention includes Al 0.65 Ga 0.35 N layer a and Al x Ga 1-x N layer b which are alternately superposed, that is, V-type Al composition graded P-type AlGaN
  • the gradient of the structure is Al 0.65 Ga 0.35 N-Al x Ga 1-x N and Al x Ga 1-x N-Al 0.65 Ga 0.35 N, the degree of gradation is As the x design value changes, the degree of gradation of the V-type Al composition graded P-type AlGaN structure can be controlled.
  • the degree of gradation of the Al composition is increased, that is, the value of x is decreased, the injection rate of carriers is increased, and the internal quantum efficiency, output power, and luminous intensity of the deep ultraviolet LED having a V-type Al composition gradient P-type AlGaN structure are increased. Both have improved.
  • the range of values of x in the Al x Ga 1-x N layer is not limited.
  • the inventors have simulated that the range of x is 0.3 ⁇ x ⁇ 0.4, and the V-type Al composition is gradually changed.
  • the thickness of each layer structure in the P-type AlGaN structure is 12.22 nm, a total of 110 nm, and the internal quantum efficiency and output power of the deep ultraviolet LED are more obviously improved.
  • the doping concentration and the Al composition of the structural layers such as the multiple quantum well structure, the P-type GaN layer, and the undoped buffer layer are not limited in the present invention.
  • the undoped buffer layer 2 is undoped Al 0.5 Ga 0.5 in this embodiment.
  • the N buffer layer had a thickness of 1.5 ⁇ m, a growth temperature of 530 ° C, and the undoped Al 0.5 Ga 0.5 N buffer layer was recrystallized at 1050 ° C for 6 minutes.
  • the composition of the N-type AlGaN layer 3 was Al 0.5 Ga 0.5 N, the thickness was 3.0 ⁇ m, the doping concentration was 5 ⁇ 10 18 cm -3 , and the growth temperature was 1050 °C.
  • the multiple quantum well structure 4 is a stacked structure of a 5-period Al 0.36 Ga 0.64 N layer and an Al 0.5 Ga 0.5 N layer, wherein the Al 0.36 Ga 0.64 N layer is in contact with the N-type AlGaN layer 4. It should be noted that, in other embodiments of the present invention, the period of the superposed structure of the Al 0.36 Ga 0.64 N layer and the Al 0.5 Ga 0.5 N layer in the multiple quantum well structure may be 5-12 cycles, which is in this embodiment. This is not limited.
  • the growth temperature of the multiple quantum well structure is 1020 ° C, wherein the thickness of each layer of Al 0.36 Ga 0.64 N is 10 nm, and the thickness of each layer of Al 0.5 Ga 0.5 N layer is 3 nm.
  • the P-type GaN layer 6 has a doping concentration of 1 ⁇ 10 18 cm -3 , a thickness of about 10 nm, a growth temperature of 990 ° C, and annealing at 700 ° C for 20 minutes.
  • the substrate is sapphire.
  • the sapphire is often used in the facets of the A side, the C side, and the R side.
  • the lattice constant ratio between the C-plane of sapphire and the deposited films of Group III-V and II-VI is small, and meets the requirements of high temperature resistance in the GaN barrier process. Therefore, in this embodiment, the The substrate is a C-plane sapphire substrate.
  • the deep ultraviolet LED provided by the embodiment of the present invention may further include a first electrode 7 and a second electrode 8, wherein the first electrode is located on the P-type GaN layer 6, and the second electrode 8 is located on the N-type AlGaN layer 3, in this embodiment
  • the material of the first electrode 7 and the second electrode 8 is not limited.
  • a V-type Al composition graded P-type AlGaN structure is disposed between the multiple quantum well structure and the P-type GaN layer. Since the V-type Al composition graded P-type AlGaN structure adopts a polarization doping method, a higher concentration of holes can be obtained, thereby increasing the hole injection rate, so that more holes are injected into the quantum well of the active region. The probability of recombination of electrons and hole radiation in the active region is improved, thereby improving the internal quantum efficiency and the transmission power of the ultraviolet LED.
  • the V-type Al composition graded P-type AlGaN structure also functions as an electron blocking layer, which can more effectively block the leakage of electrons from the active region, and further improve the internal quantum efficiency and the emission power of the ultraviolet LED.
  • the P-type AlGaN structure with V-type Al composition grading due to the P-type AlGaN structure with V-type Al composition grading, the polarization electric field in the quantum well structure of the active region can be weakened, and the quantum-confined Stark effect is weakened, thereby making more electrons and hole waves. The functions overlap, the radiative recombination in the active region is greatly increased, and the internal quantum efficiency of the ultraviolet LED is improved.
  • each layer structure can be fabricated by MOCVD (Metal-organic Chemical Vapor DePosition) equipment.
  • MOCVD Metal-organic Chemical Vapor DePosition
  • the present invention is implemented
  • An example also provides a method of fabricating the deep ultraviolet LED, comprising:
  • a sapphire substrate is placed in the reaction chamber. Then, the substrate was fired at a high temperature of 1090 ° C with high purity hydrogen.
  • a low-temperature undoped Al 0.5 Ga 0.5 N buffer layer was grown by introducing a Ga source, an Al source, and a nitrogen source at 530 ° C. The thickness of the undoped Al 0.5 Ga 0.5 N buffer layer was about 1.5 ⁇ m. Then, the temperature was raised to 1050 ° C and kept at a constant temperature for about 6 minutes to recrystallize the buffer layer.
  • a Ga source, an Al source, ammonia gas, and silane SiH 4 were introduced at 1050 ° C to grow an N-type Al 0.5 Ga 0.5 N layer having a doping concentration of 5 ⁇ 10 18 cm -3 and a thickness of 3 ⁇ m.
  • the temperature was lowered to 1020 ° C and a Ga source, an Al source, and ammonia gas were passed to grow a 10 nm thick Al 0.36 Ga 0.64 N quantum barrier.
  • a 3 nm thick Al 0.5 Ga 0.5 N quantum well was grown at 1020 °C. The first two steps were repeated to grow a total of 5 cycles of Al 0.36 Ga 0.64 N/Al 0.5 Ga 0.5 N multiple quantum well structure.
  • each layer has a thickness of 12.22 nm and a total of 110 nm.
  • the V-type Al composition graded P-type AlGaN structure is doped with polarization and has a doping concentration of 5 ⁇ 10 17 cm -3 .
  • a P-type GaN layer is grown to a thickness of 10 nm. Finally, annealing at 700 ° C for 20 minutes gave a P-type layer having a high hole concentration.
  • the specific form of the Ga source and the Al source is not limited.
  • the Ga source used in the embodiment is trimethylgallium TMGa
  • the Al source is trimethylaluminumTMAl, nitrogen.
  • the source is ammonia gas NH 3
  • the carrier gas is H 2
  • the N-type and P-type dopant sources are silane SiH 4 and ferrocene Cp 2 Mg, respectively.
  • the V-type Al composition gradient P-type AlGaN structure is obtained by polarization doping, which can obtain a higher concentration of holes, thereby increasing the hole injection rate, so that more holes are injected into the hole.
  • the probability of recombination of electrons and hole radiation in the active region is improved, thereby improving the internal quantum efficiency and the transmission power of the deep ultraviolet LED.
  • the Al composition at the interface with the last barrier layer of the quantum well starts to gradually change from 0.65, and the active region has a higher electron concentration, so that the V-type
  • the Al-graded P-type AlGaN structure also has an electron blocking layer function, which can more effectively block the leakage of electrons from the active region, thereby removing the electron blocking layer and simplifying the epitaxial structure of the deep ultraviolet LED.
  • the P-type AlGaN structure adopting the V-type Al composition gradation can weaken the polarization electric field in the quantum well structure of the active region, and weaken the quantum-confined Stark effect, thereby making more electrons and empty

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Abstract

一种深紫外LED，包括：衬底（1）；位于衬底表面的未掺杂的缓冲层（2）；位于未掺杂的缓冲层背离衬底表面的N型AlGaN层（3）；位于N型AlGaN层背离衬底表面的多量子阱结构（4）；位于多量子阱结构背离衬底表面的V型Al组分渐变的P型AlGaN结构（5），V型Al组分渐变的P型AlGaN结构采用极化掺杂，且其中V型Al组分渐变的P型AlGaN结构中的Al组分与多量子阱结构的Al组分不同；位于V型Al组分渐变的P型AlGaN结构背离衬底表面的P型GaN层（6）。由于V型Al组分渐变的P型AlGaN结构能够获得更高浓度的空穴，从而提高紫外LED的内量子效率和发射功率。

Description

一种深紫外LED 技术领域
本申请要求于2017年7月21日提交中国专利局、申请号为201710600453.1、发明名称为“一种深紫外LED”的国内申请的优先权，其全部内容通过引用结合在本申请中。
背景技术
基于AlGaN(氮化铝镓)材料的紫外LED是目前氮化物技术发展和第三代材料技术发展的主要趋势，拥有广阔的应用前景。紫外LED应用范围很广，如空气和水的净化、消毒、紫外医疗、高密度光学存储系统、全彩显示器以及固态白光照明等等。半导体紫外光源作为半导体照明后的又一重大产业，已经引起半导体光电行业的广泛关注。
但与蓝光LED不同，目前紫外LED正处于技术发展期，还存在一些难以突破的问题，如AlGaN基紫外LED的内量子效率和发射功率相对较低。
因此，如何提高AlGaN基紫外LED的内量子效率和发射功率成为亟待解决的问题。
发明内容
有鉴于此，本发明提供一种深紫外LED，以解决现有技术中深紫外LED的内量子效率和发射功率较低的问题。
为实现上述目的，本发明提供如下技术方案：
一种深紫外LED，包括：
衬底；
位于所述衬底表面的未掺杂的缓冲层；
位于所述未掺杂的缓冲层背离所述衬底表面的N型AlGaN层；
位于所述N型AlGaN层背离所述衬底表面的多量子阱结构；
位于所述多量子阱结构背离所述衬底表面的V型Al组分渐变的P型 AlGaN结构，所述V型Al组分渐变的P型AlGaN结构采用极化掺杂，且其中所述V型Al组分渐变的P型AlGaN结构中的Al组分与所述多量子阱结构的Al组分不同；
位于所述V型Al组分渐变的P型AlGaN结构背离所述衬底表面的P型GaN层。
优选地，所述V型Al组分渐变的P型AlGaN结构包括至少一层Al0.65Ga0.35N层和至少一层AlxGa1-xN层，所述Al0.65Ga0.35N层和所述AlxGa1-xN层交替叠加，其中，所述Al0.65Ga0.35N层生长在所述多量子阱结构的表面。
优选地，所述AlxGa1-xN层中的x取值范围为：0.3≤x≤0.4。
优选地，所述V型Al组分渐变的P型AlGaN结构中每层结构的厚度为12.22nm，共110nm。
优选地，所述V型Al组分渐变的P型AlGaN结构的掺杂浓度为5×1017cm-3，生长温度为990℃。
优选地，所述衬底为C面的蓝宝石衬底。
优选地，所述未掺杂的缓冲层为未掺杂的Al0.5Ga0.5N缓冲层，厚度为1.5μm，生长温度为530℃，且所述未掺杂的Al0.5Ga0.5N缓冲层在1050℃恒温6分钟重结晶。
优选地，所述N型AlGaN层为Al0.5Ga0.5N层，厚度为3.0μm，掺杂浓度为5×1018cm-3，生长温度为1050℃。
优选地，所述多量子阱结构为5个周期的Al0.36Ga0.64N层和Al0.5Ga0.5N层的叠加结构，其中，所述Al0.36Ga0.64N层生长在所述N型AlGaN层的表 面。
优选地，所述多量子阱结构的生长温度为1020℃，其中，每层所述Al0.36Ga0.64N层的厚度为10nm，每层所述Al0.5Ga0.5N层的厚度为3nm。
经由上述的技术方案可知，本发明提供的深紫外LED，在多量子阱结构与P型GaN层之间设置V型Al组分渐变的P型AlGaN结构。一方面，由于V型Al组分渐变P型AlGaN结构采用极化掺杂方式，能够获得更高浓度的空穴，从而提高空穴注入率，使得更多的空穴被注入到有源区的量子阱中，提高有源区电子与空穴辐射复合的概率，从而提高紫外LED的内量子效率和发射功率。
另一方面，本发明中V型Al组分渐变的P型AlGaN结构与多量子阱结构的最后一个垒层交界处，Al组分不同，有源区具有更高电子浓度，使得V形Al组分渐变的P型AlGaN结构也具备电子阻挡层的作用，能更有效地阻挡电子从有源区的泄露，从而可以替代电子阻挡层(EBL)，同时电子泄露减少，且空穴注入效率增加，电子与空穴的复合几率增大，进一步提高了紫外LED的内量子效率和发射功率。
再一方面，由于采用V型Al组分渐变的P型AlGaN结构，电子与空穴的浓度增加，复合概率增加。在外加电场之下，电子和空穴复合的效率增加，原本内部电子、空穴不复合的情况下形成的极化电场，由于复合且复合概率增加所以减弱。也即本发明提供的深紫外LED能够减弱有源区量子阱结构中的极化电场，减弱量子限制斯塔克效应，从而使得更多的电子和空穴波函数重叠，有源区辐射复合大大增加，紫外LED的内量子效率得到提高。
附图说明
为了更清楚地说明本发明实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本发明的实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据提供的附图获得其他的附图。
图1为本发明实施例提供的一种深紫外LED的结构示意图；
图2为本发明实施例提供的一种深紫外LED中V型Al组分渐变的P型AlGaN结构的示意图。
具体实施方式
正如背景技术部分所述，现有技术中AlGaN基紫外LED的内量子效率和发射功率相对较低。
目前AlGaN基深紫外LED光源发光效率低的原因主要有：高Al组分AlGaN材料的载流子注入效率低，制约了紫外LED内量子效率的提高；高Al组分AlGaN材料的结构性质决定其出光效率低。
基于此，本发明提供一种深紫外LED，包括：
衬底；
位于所述衬底表面的未掺杂的缓冲层；
位于所述未掺杂的缓冲层背离所述衬底表面的N型AlGaN层；
位于所述N型AlGaN层背离所述衬底表面的多量子阱结构；
位于所述多量子阱结构背离所述衬底表面的V型Al组分渐变的P型AlGaN结构，所述V型Al组分渐变的P型AlGaN结构采用极化掺杂，且其中所述V型Al组分渐变的P型AlGaN结构中的Al组分与所述多量子阱结构的Al组分不同；
位于所述V型Al组分渐变的P型AlGaN结构背离所述衬底表面的P型GaN层。
本发明提供的深紫外LED，在多量子阱结构与P型GaN层之间设置V型Al组分渐变的P型AlGaN结构。由于V型Al组分渐变P型AlGaN结构采用极化掺杂方式，能够获得更高浓度的空穴，从而提高空穴注入率，使得更多的空穴被注入到有源区的量子阱中，提高有源区电子与空穴辐射复合的概率，从而提高紫外LED的内量子效率和发射功率。另一方面，V型Al组分 渐变的P型AlGaN结构也具备电子阻挡层的作用，能更有效地阻挡电子从有源区的泄露，进一步提高了紫外LED的内量子效率和发射功率。再一方面，由于采用V型Al组分渐变的P型AlGaN结构，能够减弱有源区量子阱结构中的极化电场，减弱量子限制斯塔克效应，从而使得更多的电子和空穴波函数重叠，有源区辐射复合大大增加，紫外LED的内量子效率得到提高。
下面将结合本发明实施例中的附图，对本发明实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本发明一部分实施例，而不是全部的实施例。基于本发明中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他实施例，都属于本发明保护的范围。
请参见图1，为本发明实施例提供的一种深紫外LED，包括：衬底1；位于衬底1表面的未掺杂的缓冲层2；位于未掺杂的缓冲层2背离衬底1表面的N型AlGaN层3；位于N型AlGaN层3背离衬底1表面的多量子阱结构4；位于多量子阱结构4背离衬底表面的V型Al组分渐变的P型AlGaN结构5，V型Al组分渐变的P型AlGaN结构5采用极化掺杂，且其中，V型Al组分渐变的P型AlGaN结构5中的Al组分与多量子阱结构4的Al组分不同；位于V型Al组分渐变的P型AlGaN结构5背离衬底1表面的P型GaN层6。
需要说明的是，本发明实施例中不限定V型Al组分渐变的P型AlGaN结构的具体结构，可选的，如图2所示，V型Al组分渐变的P型AlGaN结构5包括至少一层Al0.65Ga0.35N层a和至少一层AlxGa1-xN层b，Al0.65Ga0.35N层a和AlxGa1-xN层b交替叠加，其中，Al0.65Ga0.35N层a与多量子阱结构的表面接触。也即本发明实施例提供的深紫外LED在与多量子阱的最后一个垒层交界处的Al组分是从0.65开始渐变的。
本发明实施例中V型Al组分渐变的P型AlGaN结构包括交替叠加的Al0.65Ga0.35N层a和AlxGa1-xN层b，也即V型Al组分渐变的P型AlGaN结构的渐变为Al0.65Ga0.35N-AlxGa1-xN和AlxGa1-xN-Al0.65Ga0.35N，渐变程度为
Figure PCTCN2017114551-appb-000001
随着x设计值的改变，可控制V型Al组分渐变的P型AlGaN结构的渐变程度。当增加Al组分渐变程度，即减小x的值时，载流子的注入率增加，具有V型Al组分渐变的P型AlGaN结构的深紫外LED的内量子效率、输出功率和发光强度均有所提高。
本发明中不限定AlxGa1-xN层中x的取值范围，可选的，发明人经过模拟得到当x的取值范围为0.3≤x≤0.4时，且V型Al组分渐变的P型AlGaN结构中每层结构的厚度为12.22nm，共110nm，深紫外LED的内量子效率和输出功率提高较为明显。
需要说明的是，在本发明中不限定多量子阱结构、P型GaN层、未掺杂的缓冲层等结构层的掺杂浓度和Al组分。为了在x的取值范围为0.3≤x≤0.4时，深紫外LED的内量子效率和输出功率提高较为明显，本实施例中限定未掺杂的缓冲层2为未掺杂的Al0.5Ga0.5N缓冲层，厚度为1.5μm，生长温度为530℃，且所述未掺杂的Al0.5Ga0.5N缓冲层在1050℃恒温6分钟重结晶。N型AlGaN层3的组分为Al0.5Ga0.5N，厚度为3.0μm，掺杂浓度为5×1018cm-3，生长温度为1050℃。多量子阱结构4为5个周期的Al0.36Ga0.64N层和Al0.5Ga0.5N层的叠加结构，其中，所述Al0.36Ga0.64N层与N型AlGaN层4接触。需要说明的是，在本发明的其他实施例中，多量子阱结构中Al0.36Ga0.64N层和Al0.5Ga0.5N层的叠加结构的周期可以是5-12个周期，本实施例中对此不做限定。本实施例中，多量子阱结构的生长温度为1020℃，其中，每层Al0.36Ga0.64N层的厚度为10nm，每层Al0.5Ga0.5N层的厚度为3nm。P型GaN层6的掺杂浓度为1×1018cm-3，厚度约为10nm，生长温度为990℃，并在700℃下退火20分钟。
本实施例中不限定衬底的具体材质，可以根据实际需求进行选择，需要说明的是，由于蓝宝石具有较高的透光性，本实施例中可选的，所述衬底为蓝宝石。蓝宝石常被运用的切面有A面、C面、R面。蓝宝石的C面与III-V族和II-VI族沉积薄膜之间的晶格常数适配率小，同时符合GaN垒晶制程中耐高温的要求，因此，本实施例中可选的，所述衬底为C面的蓝宝石衬底。
本发明实施例提供的深紫外LED还可以包括第一电极7和第二电极8，其中第一电极位于P型GaN层6上，第二电极8位于N型AlGaN层3上，本实施例中不限定第一电极7和第二电极8的材质。
本发明提供的深紫外LED，在多量子阱结构与P型GaN层之间设置V型Al组分渐变的P型AlGaN结构。由于V型Al组分渐变P型AlGaN结构采用极化掺杂方式，能够获得更高浓度的空穴，从而提高空穴注入率，使得更多的空穴被注入到有源区的量子阱中，提高有源区电子与空穴辐射复合的概率，从而提高紫外LED的内量子效率和发射功率。另一方面，V型Al组分渐变的P型AlGaN结构也具备电子阻挡层的作用，能更有效地阻挡电子从有源区的泄露，进一步提高了紫外LED的内量子效率和发射功率。再一方面，由于采用V型Al组分渐变的P型AlGaN结构，能够减弱有源区量子阱结构中的极化电场，减弱量子限制斯塔克效应，从而使得更多的电子和空穴波函数重叠，有源区辐射复合大大增加，紫外LED的内量子效率得到提高。
对于上述提供的深紫外LED结构，本发明不限定深紫外LED的制作方法，可选的，可以采用MOCVD(Metal-organic Chemical Vapor DePosition，金属有机化合物化学气相淀积)设备制作各层结构。具体地，本发明实施 例还提供一种制作所述深紫外LED的制作方法，包括：
首先，将蓝宝石衬底置入反应室。然后，在1090℃通高纯氢气高温灼烧衬底。接着，在530℃下通入Ga源、Al源和氮源生长低温未掺杂的Al0.5Ga0.5N缓冲层，未掺杂的Al0.5Ga0.5N缓冲层的厚度约为1.5μm。然后，升温到1050℃并恒温6分钟左右，使得缓冲层重结晶。
随后，在1050℃下通入Ga源、Al源、氨气和硅烷SiH4，生长N型Al0.5Ga0.5N层，其掺杂浓度为5×1018cm-3，厚度为3μm。
接下来，降温到1020℃并通入Ga源、Al源、氨气生长10nm厚的Al0.36Ga0.64N量子垒。接着，在1020℃生长3nm厚的Al0.5Ga0.5N量子阱。重复前两步步骤，共生长5个周期的Al0.36Ga0.64N/Al0.5Ga0.5N多量子阱结构。
紧接着，降温到990℃，通入Al源，Ga源，氨气和Mg源，生长V型Al组分渐变的P型AlGaN结构。其渐变程度为Al0.65Ga0.35N-AlxGa1-xN和AlxGa1-xN-Al0.65Ga0.35N。其中，x取值范围在0.3≤x≤0.4。V型Al组分渐变的P型AlGaN结构中，每层厚度12.22nm，共110nm。V型Al组分渐变的P型AlGaN结构采用极化掺杂，其掺杂浓度5×1017cm-3。
然后，在V型Al组分渐变的P型AlGaN结构之上，生长一层P型GaN层，厚度为10nm。最后，在700℃退火20分钟，得到高空穴浓度的P型层。
需要说明的是，本实施例中不限定Ga源、Al源的具体形式，可选的，本实施例中所采用的Ga源为三甲基镓TMGa，Al源为三甲基铝TMAl，氮源为氨气NH3，载气为H2，N型和P型掺杂源分别为硅烷SiH4和二茂镁Cp2Mg。
本发明实施例中的V型Al组分渐变的P型AlGaN结构采用极化掺杂方式得到，能够获得更高浓度的空穴，从而提高空穴注入率，使得更多的空穴被注入到有源区的量子阱中，提高有源区电子与空穴辐射复合的概率，从而提高深紫外LED的内量子效率和发射功率。
本发明实施例中由于采用V型Al组分渐变的P型AlGaN结构，与量子阱最后一个垒层交界处的Al组分是从0.65开始渐变，有源区具有更高电子浓度，使得V型Al组分渐变的P型AlGaN结构也具备电子阻挡层的作用，能更有效地阻挡电子从有源区的泄露，从而可以去掉电子阻挡层，简化深紫外LED的外延结构。
本发明实施例中由于采用采用V型Al组分渐变的P型AlGaN结构，能减弱有源区量子阱结构中的极化电场，减弱量子限制斯塔克效应，从而使得更多的电子和空穴波函数重叠，有源区辐射复合大大增加，紫外LED的内量子效率得到提高。
需要说明的是，本说明书中的各个实施例均采用递进的方式描述，每个实施例重点说明的都是与其他实施例的不同之处，各个实施例之间相同相似的部分互相参见即可。
对所公开的实施例的上述说明，使本领域专业技术人员能够实现或使用本发明。对这些实施例的多种修改对本领域的专业技术人员来说将是显而易见的，本文中所定义的一般原理可以在不脱离本发明的精神或范围的情况下，在其它实施例中实现。因此，本发明将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。

Claims (10)

  1. 一种深紫外LED，其特征在于，包括：
    衬底；
    位于所述衬底表面的未掺杂的缓冲层；
    位于所述未掺杂的缓冲层背离所述衬底表面的N型AlGaN层；
    位于所述N型AlGaN层背离所述衬底表面的多量子阱结构；
    位于所述多量子阱结构背离所述衬底表面的V型Al组分渐变的P型AlGaN结构，所述V型Al组分渐变的P型AlGaN结构采用极化掺杂，且其中所述V型Al组分渐变的P型AlGaN结构中的Al组分与所述多量子阱结构的Al组分不同；
    位于所述V型Al组分渐变的P型AlGaN结构背离所述衬底表面的P型GaN层。
  2. 根据权利要求1所述的深紫外LED，其特征在于，所述V型Al组分渐变的P型AlGaN结构包括至少一层Al0.65Ga0.35N层和至少一层AlxGa1-xN层，所述Al0.65Ga0.35N层和所述AlxGa1-xN层交替叠加，其中，所述Al0.65Ga0.35N层生长在所述多量子阱结构的表面。
  3. 根据权利要求2所述的深紫外LED，其特征在于，所述AlxGa1-xN层中的x取值范围为：0.3≤x≤0.4。
  4. 根据权利要求3所述的深紫外LED，其特征在于，所述V型Al组分渐变的P型AlGaN结构中每层结构的厚度为12.22nm，共110nm。
  5. 根据权利要求4所述的深紫外LED，其特征在于，所述V型Al 组分渐变的P型AlGaN结构的掺杂浓度为5×1017cm-3，生长温度为990℃。
  6. 根据权利要求1-5任意一项所述的深紫外LED，其特征在于，所述衬底为C面的蓝宝石衬底。
  7. 根据权利要求1-5任意一项所述的深紫外LED，其特征在于，所述未掺杂的缓冲层为未掺杂的Al0.5Ga0.5N缓冲层，厚度为1.5μm，生长温度为530℃，且所述未掺杂的Al0.5Ga0.5N缓冲层在1050℃恒温6分钟重结晶。
  8. 根据权利要求1-5任意一项所述的深紫外LED，其特征在于，所述N型AlGaN层为Al0.5Ga0.5N层，厚度为3.0μm，掺杂浓度为5×1018cm-3，生长温度为1050℃。
  9. 根据权利要求1-5任意一项所述的深紫外LED，其特征在于，所述多量子阱结构为5个周期的Al0.36Ga0.64N层和Al0.5Ga0.5N层的叠加结构，其中，所述Al0.36Ga0.64N层生长在所述N型AlGaN层的表面。
  10. 根据权利要求9所述的深紫外LED，其特征在于，所述多量子阱结构的生长温度为1020℃，其中，每层所述Al0.36Ga0.64N层的厚度为10nm，每层所述Al0.5Ga0.5N层的厚度为3nm。
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