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Ultra-wide bandgap semiconductor of β-Ga2O3 and its research progress of deep ultraviolet transparent electrode and solar-blind photodetector

## Ultra-wide bandgap semiconductor of β-Ga2O3 and its research progress of deep ultraviolet transparent electrode and solar-blind photodetector

Guo Dao-You, Li Pei-Gang, Chen Zheng-Wei, Wu Zhen-Ping, Tang Wei-Hua
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• #### Abstract

Gallium oxide (Ga2O3), with a bandgap of about 4.9 eV, is a new type of ultra-wide bandgap semiconductor material. The Ga2O3 can crystallize into five different phases, i.e. α, β, γ, δ, and ε-phase. Among them, the monoclinic β-Ga2O3 (space group: C2/m) with the lattice parameters of a = 12.23 Å, b = 3.04 Å, c = 5.80 Å, and β = 103.7° has been recognized as the most stable phase. The β-Ga2O3 can be grown in bulk form from edge-defined film-fed growth with a low-cost method. With a high theoretical breakdown electrical field (8 MV/cm) and large Baliga’s figure of merit, the β-Ga2O3 is a potential candidate material for next-generation high-power electronics (including diode and field effect transistor) and extreme environment electronics [high temperature, high radiation, and high voltage (low power) switching]. Due to a high transmittance to the deep ultraviolet-visible light with a wavelength longer than 253 nm, the β-Ga2O3 is a natural material for solar-blind ultraviolet detection and deep-ultraviolet transparent conductive electrode. In this paper, the crystal structure, physical properties and device applications of Ga2O3 material are introduced. And the latest research progress of β-Ga2O3 in deep ultraviolet transparent conductive electrode and solar-blind ultraviolet photodetector are reviewed. Although Sn doped Ga2O3 thin film has a conductivity of up to 32.3 S/cm and a transmittance greater than 88%, there is still a long way to go for commercial transparent conductive electrode. At the same time, the development history of β-Ga2O3 solar-blind ultraviolet photodetectors based on material type (nanometer, single crystal and thin film) is described in chronological order. The photodetector based on quasi-two-dimensional β-Ga2O3 flakes shows the highest responsivity (1.8 × 105 A/W). The photodetector based on ZnO/Ga2O3 core/shell micron-wire has a best comprehensive performance, which exhibits a responsivity of 1.3 × 103 A/W and a response time ranging from 20 ${\text{μ}}{\rm{s}}$ to 254 nm light at –6 V. We look forward to applying the β-Ga2O3 based solar-blind ultraviolet photodetectors to military (such as: missile early warning and tracking, ultraviolet communication, harbor fog navigation, and so on) and civilian fields (such as ozone hole monitoring, disinfection and sterilization ultraviolet intensity monitoring, high voltage corona detection, forest fire ultraviolet monitoring, and so on).

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• 图 1  Ga2O3几个同分异构体的晶体结构

Figure 1.  Crystal structures of several isomers of Ga2O3

图 2  Ga2O3各同分异构体的相互转换关系[4]

Figure 2.  Interconversion relation of Ga2O3 isomers[4]

图 3  β-Ga2O3的晶体结构及晶格常数[2123]

Figure 3.  Crystal structure and lattice constant of β-Ga2O3[2123]

图 4  β-Ga2O3材料具有的物理性质及其对应的器件应用

Figure 4.  Physical properties and device applications of β-Ga2O3 material

图 5  (a)在不同温度下制备获得的Sn掺杂β-Ga2O3薄膜的透过率[75]; (b) Sn掺杂β-Ga2O3薄膜的导电率随沉积温度的变化关系[24]

Figure 5.  (a) The transmittance of Sn-doped-Ga2O3 thin films prepared at different temperatures[75]; (b) the relationship between the conductivity of Sn doped -Ga2O3 thin films and the deposition temperature[24]

图 6  Sn掺杂Ga2O3薄膜的透过率和带隙(a)[81]及电阻率(b)[82]随Sn掺杂浓度的变化关系

Figure 6.  The relationship of the transmittance (a)[81], the band gap (a)[81], the resistivity (b)[82] with Sn different doping concentration in Sn-doped Ga2O3 thin films

图 7  ITO与Ga2O3:ITO薄膜性能对比　(a)光输出功率–电流–电压特征曲线; (b)近紫外LED的电致发光光谱[85]

Figure 7.  (a) Current versus light output power and forward voltage (L-I-V) characteristic curves and (b) typical electroluminescence spectra measured for near-ultraviolet LEDs with Ga2O3:ITO and ITO transparent conducting electrodes; the inset shows top-view SEM image of near-ultraviolet[85]

图 8  Au-Ga2O3纳米线-Au光电探测器　(a)黑暗情况下的I–V特性曲线及其器件结构SEM图(插图); (b)–8 V偏压下对254 nm光的I–t响应特性曲线[91]

Figure 8.  Au-Ga2O3 nanowire-Au photodetector: (a) I-V characteristic curve of the detector in dark. The inset of is a typical SEM image of the device, the scale bar: 200 nm; (b) real-time photoresponse of the detector to 254 nm light[91]

图 9  β-Ga2O3纳米桥光电探测器的日盲光电性质　(a) 器件的结构示意图; (b) 50 V偏压下对254 nm光的I–t响应特性; (c) 黑暗及对365和254 nm光响应的I–V特性曲线; (d) 不同波长的光谱响应特性[88]

Figure 9.  Solar blind photoelectric properties of photodetector based on the bridged β-Ga2O3 nanowires: (a) Schematic diagram of the devices; (b) time-dependent photoresponse of the bridged β-Ga2O3 nanowires measured in dry air under UVC (～2 mW cm–2 at 254 nm) illumination with a period of 60 s at a bias voltage of 50 V; (c) I-V characteristics of the bridged β-Ga2O3 nanowires in dark (squares), under 365 nm light (triangles), and under 254 nm light (circles). The I-V curve measured under 254 nm light is plotted on a linear scale in the inset; (d) spectral response of the bridged β-Ga2O3 nanowires revealing that the device is blind to solar light. The dashed line indicates the lowest wavelength of the solar spectrum on Earth[88]

图 10  (a) Ga2O3纳米线光电探测器在不同偏压下的光谱响应[92]; (b)在Cr/Au电极上生长获得的Ga2O3纳米线光电探测器结构[93]; (c)不同温度下生长的Ga2O3纳米线对255 nm光的I–t响应曲线[93]; (d)不同偏压下的光谱响应[93]

Figure 10.  (a) Room-temperature spectral responses of the Ga2O3 nanowires photodetector measured with different applied biases[92]; (b) Ga2O3 nanowire photodetector with Cr/Au as electrodes[93]; (c) transit responses measured from the three fabricated photodetectors grown at different temperatures[93]; (d) room-temperature spectral responses of the photodetector under different bias[93]

图 11  (a)单条Ga2O3纳米带光电探测器的SEM图[94]; (b)不同带宽Ga2O3纳米带的光谱响应, 插图为探测器结构[94]; (c) In掺杂的Ga2O3单条纳米带光电探测器的光谱响应[95]; (d)纯Ga2O3和In:Ga2O3单条纳米带黑暗情况及在250 nm光照下的I–V曲线[95]

Figure 11.  (a) SEM image of a Ga2O3 individual-nanobelt device[94]; (b) spectral response of the devices (nanobelts with different widths of 800 nm and 1.6 mm) measured at a bias of 15 V. The schematic configuration of a photoconductive measurement is inserted in the top-right corner[94]; (c) spectral response of an individual In-doped Ga2O3 nanobelt photodetector. The inset is a typical SEM image of an individual In-doped Ga2O3 nanobelt device[95]; (d) logarithmic plot of I-V curves of the individual Ga2O3 and In-doped Ga2O3 nanobelt photodetector under illumination with the 250 nm wavelength light and in dark conditions[95]

图 12  (a) Ga2O3纳米花的SEM图; (b) Ga2O3纳米花对254 nm光的I–t响应曲线[97]

Figure 12.  (a) SEM image of Ga2O3 nanoflowers; (b) I-t response curve of Ga2O3 nanoflowers to 254 nm light[97]

图 13  ZnO/Ga2O3核/壳结构的日盲紫外探测器　(a)器件示意图; (b)黑暗和254 nm光照下的I–V特征曲线; (c)–6 V偏压下的光谱响应[100]; (d)0 V偏压下的光谱响应; (e)光电流衰减[101]. Au/Ga2O3纳米线Schottky型垂直结构的光电探测器 (f)器件示意图; (g)光谱响应; (h)光电流衰减[102]

Figure 13.  Solar-blind ultraviolet photodetector based on Single ZnO-Ga2O3 core-shell microwire ZnO/Ga2O3 core-shell: (a) Device schematic diagram; (b)I-V characteristic curve in dark and under 254 nm light; (c) spectral response of the device at −6 V bias[100]; (d) the photoresponse spectrum of the device at 0 V; (e) the time response under the excitation of 266 nm pulse laser at 0 V[101]. Au/Ga2O3 nanowire Schottky vertical structure photodetector: (f) device schematic diagram; (g) spectral responses of the device at zero bias and under reverse bias of 10 V. Inset shows the responsivity of photodetectors at the wavelength of 254 nm as a function of reverse bias; (h) decay edge of the current response at reverse bias of 10 V[102].

图 14  基于β-Ga2O3薄片的日盲紫外探测器　(a)机械剥离获得β-Ga2O3微米薄片及器件制作流程示意图; (b)器件的光学照片; (c)不同波长光照下的器件的I–t响应曲线; (d) 光谱响应曲线[103]; (e) β-Ga2O3微米薄片的反应离子刻蚀减薄[104]; (f) Ni/Au电极与β-Ga2O3薄片构成的MSM结构肖特基结日盲紫外探测器在不用波长下的I–V曲线; (g)能带结构示意图[105]; (h), (i)石墨烯电极与β-Ga2O3薄片构成的MSM结构日盲紫外探测器的SEM图[106]

Figure 14.  Solar-blind ultraviolet photodetector based on β-Ga2O3 flake: (a) Schematic of the entire exfoliated β-Ga2O3 flake based photodetector fabrication process; (b) optical image of the fabricated photodetector; (c) time-dependent photoresponse of the fabricated photodetector under various illumination conditions (254, 365, 532 and 650 nm light exposure); (d) responsivity as a function of wavelength[103]; (e) the reactive ion etching assisted thinning of a β-Ga2O3 flake[104]; (f) the I-V curve; (g) energy band structure diagram of the schottky junction MSM structure solar-blind ultraviolet photodetector based on Ni/Au electrodes and β-Ga2O3 flake under different wavelengths[105]; (h), (i) the SEM image of the MSM structure solar-blind ultraviolet photodetector based on graphene electrode and β-Ga2O3 flake[106]

图 15  垂直结构肖特基型β-Ga2O3单晶日盲紫外探测器　(a)制作过程[109]; (b)光谱响应[109]; (c)实物图[89]; (d)瞬态光响应[89]

Figure 15.  Vertical solar-blind deep-ultraviolet schottky photodetectors based onβ-Ga2O3 substrates: (a) Fabrication process for photodetector[109]; (b) spectral responser[109]; (c) photograph of the flame detector. The dashed circles are on the edges of the transparent electrodes[89]; (d) transient response of the detector[89]

图 16  (a) β-Ga2O3单晶与Au电极在不同温度下退火后的I–V曲线[110]; (b)未退火和400℃下退火后Au/β-Ga2O3单晶肖特基型光电探测器的光谱响应[110]; (c)在β-Ga2O3单晶上采用溶胶凝胶法制备高绝缘β-Ga2O3薄膜并与Au电极构成的光电探测器[111]; (d)有无高绝缘β-Ga2O3薄膜层的光谱响应对比图[111]

Figure 16.  (a) Dark I-V characteristics of the Au-Ga2O3 Schottky photodiode annealed at various temperatures. The inset shows the device configuration[110]; (b) spectral response of the Au-Ga2O3 Schottky photodiode before and after annealing at 400℃. The inset shows the reverse I-V characteristics of the photodiode annealed at 400℃ taken in dark and under illumination with 240 nm light[110]; (c) schematic structure of a photodiode composed of a Au Schottky contact and a β-Ga2O3 single-crystal substrate with a sol-gel prepared cap layer.[111]; (d) spectral response of Ga2O3 photodiodes with and without a cap layer at reverse and forward biases of 3 V. The inset shows the incident light intensity dependence of the photocurrent at forward and reverse biases of 3 V under illumination with 250 nm light[111]

图 17  石墨烯/β-Ga2O3单晶日盲紫外探测器[112]　(a)器件结构示意图; (b)黑暗及365 nm光照下的I–V曲线; (c)光谱响应; (d)能带结构示意图

Figure 17.  Solar-blind ultraviolet photodetectors based on graphene/β-Ga2O3 single crystal heterojunction[112]: (a) Schematic diagram of device structure; (b) I-V characteristics of the photodetectors in dark and under 365 nm light irradiation; (c) normalized spectral selectivity; (b) energy band diagram at forward bias voltage

图 18  (a) Ga2O3薄膜的面内XRD图; (b) Ga2O3薄膜在黑暗及不同光照下的I–V曲线[90]

Figure 18.  (a) In-plane XRD measurement results for the Ga2O3 film; (b) I-V characteristics of the Ga2O3 film photodetector in the dark, under black light irradiation, and under low-pressure mercury lamp irradiation[90]

图 19  (a) Ga2O3/GaN光电探测器结构; (b) Ga2O3/GaN光电探测器在不同偏压下的光谱响应[117]; (c) Ga2O3/AlGaN/GaN光电探测器结构; (d) Ga2O3/AlGaN/GaN光电探测器在不同偏压下的光谱响应[118]; (e) Ga2O3/InGaN/GaN光电探测器结构; (f) Ga2O3/InGaN/GaN光电探测器在不同偏压下的光谱响应[119]; (g)有无Au纳米颗粒与Ga2O3界面形成的能带结构示意图; (h) Au纳米颗粒/Ga2O3光电探测器在不同偏压下的光谱响应[120]

Figure 19.  Schematic diagram (a) and spectral responses under different bias (b) of Ga2O3/GaN photodetector[117]; Schematic diagram (c) and spectral responses under different bias (d) of Ga2O3/AlGaN/GaN photodetector[118]; Schematic diagram (e) and spectral responses under different bias (f) of Ga2O3/InGaN/GaN photodetector[119]; Energy band diagram of area near the surface of β-Ga2O3 and Au in the dark (g), spectral responses under different bias of Ga2O3/GaN-based metal-semiconductor-metal photodetectors covered with Au nanoparticles (h)[120]

图 20  (a) Ga2O3/SiC光电探测器结构; (b) Ga2O3/SiC光电探测器在2 V反偏压下的光谱响应[121]

Figure 20.  Schematic diagram (a) and spectral responses under 2 V reverse bias (b) of SiC/Ga2O3 photodetector[121]

图 21  (a) Ga2O3薄膜MSM结构日盲紫外探测器的结构示意图[123]; (b) MSM结构中Ga2O3薄膜厚度对探测器光暗比的影响[124]; (c), (d) MSM结构阵列探测器[125]; (e)氧气氛退火处理构成的肖特基结与未退火欧姆接触MSM结构探测器的I–t曲线[126]. 不同元素掺杂Ga2O3薄膜MSM结构探测器的I–t曲线 (f) Mg掺杂[128]; (g) Mn掺杂[127]; (h) Zn掺杂[129]; (i) Sn掺杂[130]

Figure 21.  (a) Schematic diagram of the β-Ga2O3 thin film MSM structure photodetector[123; (b) the effect of Ga2O3 film thickness on light-dark ratio of the MSM structure photodetector[124]; (c), (d) MSM structure arrays photodetector[125]; (e)I-t curves of the β-Ga2O3 thin films MSM structure photodetector with unannealed (Ohmic-type up) and annealed treatment in O2 atmosphere (Schottky-type, down), respectively[126]. I-t curves of the MSM structure photodetector based on β-Ga2O3 thin films doped with different element: (f) Mg doped[128]; (g) Mn doped[127]; (h) Zn doped[129]; (i) Sn doped[130]

图 22  石墨烯/Ga2O3/石墨烯垂直结构日盲紫外探测器的结构示意图[138](a)及其不同偏压下对254 nm紫外光的响应度(b)[138]; 纯Ga2O3及表面附着有Au纳米颗粒Ga2O3薄膜的紫外可见吸收(c)[139]和不同光照下的I–V曲线(d)[139]; 引入Al2O3薄层生长获得的Ga2O3薄膜/纳米线SEM图(e)[140]和不同光照下的I–V曲线(f)[140]

Figure 22.  Schematic diagram (a) [138] and photoresponses to 254 nm ultraviolet light under different bias (b) [138] of graphene/Ga2O3/graphene vertical structure photodetector; UV-vis absorbance spectrum (c) [139] and I-V cures under the different wavelength light illumination (d) [139] of the bare Ga2O3 thin film and Au nanoparticles/Ga2O3 composite thin film; SEM image (e) and I-V cures under the different wavelength light illumination (f) [140] of Ga2O3 thin film/nanowire grown induced by Al2O3 thin layer[140]

图 23  Ga2O3/NSTO异质结自供电探测器的结构示意图(a)[142] 、黑暗及254 nm不同光强下的I–V曲线(b)[142]和异质结界面处光生载流子输运的能带结构示意图(c)[142]; Ga2O3/P-Si PN结探测器的结构示意图(d)[143]; Ga2O3/Ga:ZnO异质结探测器的整流特性及结构示意图(e)[145]和光谱响应(f)[145]; Ga2O3/GaN PN结探测器的结构示意图(g)[146]和黑暗及不同波长光照下的I–V曲线(h)[146]; Sn:Ga2O3/GaN PN结探测器的光谱响应(i)[144]和不同波长光照下的I–t曲线(j)[147]; Ga2O3/SiC/P-Si PIN结(k)[148]和石墨烯/Ga2O3/SiC探测器的结构示意图(l)[149]

Figure 23.  Schematic diagram (a) [142], I-V cures in dark and under 254 nm with different light intensity illumination (b) [142], and schematic energy band diagrams (c) [142] of the β-Ga2O3/NSTO heterojunction self-powered photodetector; Schematic diagram of Ga2O3/P-Si PN junction detector (d) [143]; Rectifier features (e), schematic diagram (e) and spectral response (f) of the Ga2O3/Ga:ZnO heterojunction photodetector[145]; Schematic diagram (g) [145], I-V cures in dark and under the different wavelength light illumination (h) [146]; Spectral response (i) and I-t cures under the different wavelength light illumination (j) of the Sn:Ga2O3/GaN PN junction photodetector[145]; Schematic diagram of Ga2O3/SiC/P-Si PIN junction photodetector (k) [148]and graphene/Ga2O3/SiC photodetector (l)[149]

图 24  a-GaOx非晶薄膜和β-Ga2O3薄膜日盲紫外探测器[159]　(a) MSM结构示意图; (b)光谱响应; (c)能带结构示意图

Figure 24.  Solar-blind ultraviolet photodetector based on a-GaOx amorphous film and β-Ga2O3 film[159]: (a) MSM structure diagram; (b) spectral response; (c) energy band structure diagram

图 25  MSM结构日盲紫外探测器　(a) MSM结构示意图[160]; (b) Ga2O3单晶和薄膜的光谱响应对比[160]; (c) MSM结构[162]; (d) Ga2O3薄膜不同气氛退火的光谱响应对比[161]; (e)不同氧压下生长的Ga2O3薄膜的光谱响应对比[162]; (f)不同In掺杂的Ga2O3薄膜的光谱响应对比图[163]

Figure 25.  MSM structure solar-blind ultraviolet photodetector: (a) Schematic diagram of MSM structure[160]; (b) spectral response comparison of Ga2O3 single crystal and thin film[160]; (c) MSM structure[162]; (d) spectral response comparison of Ga2O3 thin films annealed in different atmospheres[161]; (e) spectral response comparison of Ga2O3 thin films grown under different oxygen pressures[162]; (f) spectral response comparison of Ga2O3 thin films doped with different concentrations of In elements[163]

图 26  a-Ga2O3非晶薄膜日盲紫外探测器[169]　(a)以石英为衬底的器件结构示意图; (b)光谱响应; (c)光衰减测试; (d)以柔性为衬底的器件结构示意图

Figure 26.  Solar-blind ultraviolet photodetector based on a-Ga2O3 amorphous film[169]: (a) Schematic diagram of device structure with quartz substrate; (b) spectral response; (c) the decay of photoresponse; (d) schematic diagram of device structure with flexible substrate

图 27  a-GaOx非晶薄膜日盲紫外探测器[171]　(a)以玻璃为衬底的器件结构示意图; (b)黑暗和253 nm光照下的I–V曲线; 以聚酰亚胺为衬底的器件结构示意图(c)及黑暗和253 nm光照下的I–V曲线(d)

Figure 27.  Solar-blind ultraviolet photodetector based on a-Ga2O3 amorphous film[171]: Schematic diagram of device structure with glass substrate (a) and I-V cures in dark and under the illumination of 253 nm light (b); Schematic diagram of device structure with polyimide substrate (c) and I-V cures in dark and under the illumination of 253 nm light (d)

图 28  α-Ga2O3/ZnO异质结日盲紫外探测器[172]　(a)光谱响应; (b)增益随偏压的变化; (c)瞬态光响应特性; (d)能带结构及器件结构示意图

Figure 28.  Solar-blind ultraviolet photodetector based on α-Ga2O3/ZnO heterojunction[172] : (a) Spectral response; (b) variation of gain with bias; (c) transient photoresponse characteristics; (d) schematic diagram of energy band structure and device structure

图 29  以N2O为反应气体获得的β-Ga2O3薄膜日盲紫外探测器　(a)生长原理示意图[176]; (b)黑暗和255 nm光照下的I–V曲线及MSM结构示意图[176]; (c)光谱响应及不同偏压下的光响应度[176]; (d)石墨烯/β-Ga2O3/GaN器件结构示意图[177]; (e)光谱响应[177]; (f)能带结构示意图[177]

Figure 29.  Solar-blind ultraviolet photodetector based on β-Ga2O3 thin film grown using N2O as the reaction gas: (a) Schematic diagram of growth principle[176]; (b) I-V cures in dark and under 255 nm light illumination, and schematic diagram of MSM structure[176]; (c) spectral response and photoresponsivity under different bias[176]; (d) schematic diagram of graphene/β-Ga2O3/GaN devices[177]; (e) spectral response[177]; (f) energy band structure diagram[177]

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•  Citation:
##### Metrics
• Abstract views:  122
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##### Publishing process
• Received Date:  15 October 2018
• Accepted Date:  30 January 2019
• Available Online:  06 June 2019
• Published Online:  01 April 2019

## Ultra-wide bandgap semiconductor of β-Ga2O3 and its research progress of deep ultraviolet transparent electrode and solar-blind photodetector

###### Corresponding author: Tang Wei-Hua, whtang@bupt.edu.cn
• 1. Center for Optoelectronics Materials and Devices, Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018, China
• 2. Laboratory of Information Functional Materials and Devices, School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China
• 3. State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876, China

Abstract: Gallium oxide (Ga2O3), with a bandgap of about 4.9 eV, is a new type of ultra-wide bandgap semiconductor material. The Ga2O3 can crystallize into five different phases, i.e. α, β, γ, δ, and ε-phase. Among them, the monoclinic β-Ga2O3 (space group: C2/m) with the lattice parameters of a = 12.23 Å, b = 3.04 Å, c = 5.80 Å, and β = 103.7° has been recognized as the most stable phase. The β-Ga2O3 can be grown in bulk form from edge-defined film-fed growth with a low-cost method. With a high theoretical breakdown electrical field (8 MV/cm) and large Baliga’s figure of merit, the β-Ga2O3 is a potential candidate material for next-generation high-power electronics (including diode and field effect transistor) and extreme environment electronics [high temperature, high radiation, and high voltage (low power) switching]. Due to a high transmittance to the deep ultraviolet-visible light with a wavelength longer than 253 nm, the β-Ga2O3 is a natural material for solar-blind ultraviolet detection and deep-ultraviolet transparent conductive electrode. In this paper, the crystal structure, physical properties and device applications of Ga2O3 material are introduced. And the latest research progress of β-Ga2O3 in deep ultraviolet transparent conductive electrode and solar-blind ultraviolet photodetector are reviewed. Although Sn doped Ga2O3 thin film has a conductivity of up to 32.3 S/cm and a transmittance greater than 88%, there is still a long way to go for commercial transparent conductive electrode. At the same time, the development history of β-Ga2O3 solar-blind ultraviolet photodetectors based on material type (nanometer, single crystal and thin film) is described in chronological order. The photodetector based on quasi-two-dimensional β-Ga2O3 flakes shows the highest responsivity (1.8 × 105 A/W). The photodetector based on ZnO/Ga2O3 core/shell micron-wire has a best comprehensive performance, which exhibits a responsivity of 1.3 × 103 A/W and a response time ranging from 20 ${\text{μ}}{\rm{s}}$ to 254 nm light at –6 V. We look forward to applying the β-Ga2O3 based solar-blind ultraviolet photodetectors to military (such as: missile early warning and tracking, ultraviolet communication, harbor fog navigation, and so on) and civilian fields (such as ozone hole monitoring, disinfection and sterilization ultraviolet intensity monitoring, high voltage corona detection, forest fire ultraviolet monitoring, and so on).

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