Transition of photoconductive and photovoltaic operation modes in amorphous Ga2O3-based solar-blind detectors tuned by oxygen vacancies**Project supported by the National Key Research and Development Project, China (Grant No. 2017YFB0403003), the National Natural Science Foundation of China (Grant Nos. 61774081, 61322403, and 91850112), the State Key Research and Development Project of Jiangsu Province, China (Grant No. BE2018115), Shenzhen Fundamental Research Project, China (Grant Nos. 201773239 and 201888588), the Project of the State Key Laboratory of Wide-Bandgap Semiconductor Power Electric Devices, China (Grant No. 2017KF001), and the Fundamental Research Funds for the Central Universities, China (Grant Nos. 021014380093 and 021014380085).

Abstract

We report on the transition of photovoltaic and photoconductive operation modes of the amorphous Ga2O3-based solar-blind photodetectors in metal–semiconductor–metal (MSM) configurations. The conversion from Ohmic to Schottky contacts at Ti/Ga2O3 interface is realized by tuning the conductivity of amorphous Ga2O3 films with delicate control of oxygen flux in the sputtering process. The abundant donor-like oxygen vacancies distributed near the Ti/Ga2O3 interface fascinate the tunneling process across the barrier and result in the formation of Ohmic contacts. As a consequence, the serious sub-gap absorption and persistent photoconductivity (PPC) effect degrades the performance of the photoconductive detectors. In contrast, the photovoltaic device with a Schottky contact exhibits an ultra-low dark current less than 1 pA, a high detectivity of , a fast response time of , and a high ultraviolet C (UVC)-to-ultraviolet A (UVA) rejection ratio of 103. The promoting performance is attributed primarily to the reduction of the sub-gap states and the resultant suppression of PPC effect. With simple architecture, low fabrication cost, and easy fusion with modern high-speed integrated circuitry, these results provide a cost-effective way to realize high performance solar-blind photodetectors towards versatile practical applications.