Fig. 1. Crystal structures of several isomers of Ga₂O₃Ga₂O₃几个同分异构体的晶体结构

Fig. 2. Interconversion relation of Ga₂O₃ isomers^[4]Ga₂O₃各同分异构体的相互转换关系^[4]

Fig. 3. Crystal structure and lattice constant of β-Ga₂O₃^[21−23]β-Ga₂O₃的晶体结构及晶格常数^[21−23]

Fig. 4. Physical properties and device applications of β-Ga₂O₃ material β-Ga₂O₃材料具有的物理性质及其对应的器件应用

Fig. 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](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]

Fig. 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 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

Fig. 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]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]

Fig. 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]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]

Fig. 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]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]

Fig. 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](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]

Fig. 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](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]

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

Fig. 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]. 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]

Fig. 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]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]

Fig. 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]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]

Fig. 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](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]

Fig. 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 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

Fig. 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](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]

Fig. 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](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]

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

Fig. 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](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]

Fig. 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]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]

Fig. 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]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]

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

Fig. 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]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]

Fig. 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 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

Fig. 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) a-GaO_x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)

Fig. 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 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

Fig. 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]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]