In recent years, Ga2O3 solar-blind photodetectors (SBPDs) have received great attention for their potential applications in solar-blind imaging, deep space exploration, confidential space communication, etc. In this work, we demonstrated an ultra-high-performance ε-Ga2O3 metal–semiconductor–metal (MSM) SBPD. The fabricated photodetectors exhibited a record-high responsivity and fast decay time of 230 A/W and 24 ms, respectively, compared with MSM-structured Ga2O3 photodetectors reported to date. Additionally, the ε-Ga2O3 MSM SBPD presents an ultrahigh detectivity of 1.2 × 1015 Jones with a low dark current of 23.5 pA under an operation voltage of 6 V, suggesting its strong capability of detecting an ultraweak signal. The high sensitivity and wavelength selectivity of the photodetector were further confirmed by the record-high responsivity rejection ratio (R 250 nm/R 400 nm) of 1.2 × 105. From the temperature-dependent electrical characteristics in the dark, the thermionic field emission and Poole–Frenkel emission were found to be responsible for the current transport in the low and high electric field regimes, respectively. In addition, the gain mechanism was revealed by the Schottky barrier lowering effect due to the defect states at the interface of the metal contact and Ga2O3 or in the bulk of Ga2O3 based on current transport mechanism and density functional theory calculations. These results facilitate a better understanding of ε-Ga2O3 photoelectronic devices and provide possible guidance for promoting their performance in future solar-blind detection applications.

Gallium oxide (Ga2O3) is a new semiconductor material which has the advantage of ultrawide bandgap, high breakdown electric field, and large Baliga’s figure of merit (BFOM), so it is a promising candidate for the next-generation high-power devices including Schottky barrier diode (SBD). In this paper, the basic physical properties of Ga2O3 semiconductor have been analyzed. And the recent investigations on the Ga2O3-based SBD have been reviewed. Meanwhile, various methods for improving the performances including breakdown voltage and on-resistance have been summarized and compared. Finally, the prospect of Ga2O3-based SBD for power electronics application has been analyzed.

In this Letter, we report a high-performance NiO/β-Ga2O3 pn heterojunction diode with an optimized interface by annealing. The electrical characteristics of the pn diode without annealing (PND) and with annealing (APND) are studied systematically. The APND device has a lower specific on-resistance of 4.1 mΩ cm2, compared to that of the PND, 5.4 mΩ cm2. Moreover, for the APND, a high breakdown voltage of 1630 V with lower leakage current is achieved, which is 730 V higher than that of the PND. The enhanced electrical performance of the APND leads to a record high power figure of merit of 0.65 GW/cm2 in Ga2O3-based pn diodes, which is among the best reported results in Ga2O3 power devices. In addition, the interface trap density of the diode decreases from 1.04 × 1012 to 1.33 × 1011 eV−1 cm−2 after annealing, contributing to much lower hysteresis. Simultaneously, the ideality factor n for the APND is steady at elevated temperatures due to the stable interface. The results of C−V characteristics reveal the bulk defects inside the nickel oxide film grown by sputtering, which are calculated by high- and low-frequency capacitance methods. X-ray photoelectron spectroscopy of NiO illustrates the reasons for the changes in the concentration of holes and defects in the film before and after annealing. This work paves the way for further improving the performance of Ga2O3 diode via interface engineering.

Ga2O3‐based solar‐blind photodetectors (PDs) are now attracting more and more attention for their potential application in optical imaging, spatial communication, etc. However, the performance of ever‐reported Ga2O3‐based PDs is still not good enough, strongly affected by either the Ga2O3 crystalline quality or the device structure, which severely limits their capability to detect extremely weak signals and achieve future applications. In this work, solar‐blind field‐effect phototransistor based on radio‐frequency‐magnetron sputtered amorphous gallium oxide thin film with ultrahigh photodetection performance are demonstrated. The key feature of the device is gate‐tunable photodetection enabling ultrahigh responsivity of 4.1 × 103 A W−1, external quantum efficiency of 2 × 106%, and detectivity of 2.5 × 1013 Jones under a 70 µW cm−2 weak signal of 254 nm light due to a high internal gain and field effect control of the phototransistor. Furthermore, high‐resolution imaging is achieved for the imaging target by integrating the as‐fabricated photodetectors into the imaging system, which is the first report on solar‐blind imaging of amorphous gallium oxide photodetectors. Such field‐effect phototransistors with ultrahigh performance and excellent imaging capability address a significant step toward the feasibility and practicability of gallium oxide photodetectors in solar‐blind imaging system.

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Ultraviolet (UV) photodetectors (PDs) have drawn great attention in recent years due to their potential application in civil and military fields. Because of its ultrawide bandgap, low cost, strong radiation hardness, and high thermal and chemical stability with high visible-light transparency, Ga 2 O 3 is regarded as the most promising candidate for UV detection. Furthermore, the bandgap of Ga 2 O 3 is as high as 4.7-4.9 eV, directly corresponding to the solar-blind UV detection band with wavelength less than 280 nm. There is no need of doping in Ga 2 O 3 to tune its bandgap, compared to AlGaN, MgZnO, etc, thereby avoiding alloy composition fluctuations and phase separation. At present, solar-blind Ga 2 O 3 photodetectors based on single crystal or amorphous Ga 2 O 3 are mainly focused on metal-semiconductor-metal and Schottky photodiodes. In this work, the recent achievements of Ga 2 O 3 photodetectors are systematically reviewed. The characteristics and performances of different photodetector structures based on single crystal Ga 2 O 3 and amorphous Ga 2 O 3 thin film are analyzed and compared. Finally, the prospects of Ga 2 O 3 UV photodetectors are forecast.

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