Epitaxial growth of ε-(AlGa)<sub>2</sub>O<sub>3</sub> films on sapphire substrate by PLD and the fabrication of photodetectors
Yangyang Gao, Qian Feng, Zhaoqing Feng, Yan Zuo, Yuncong Cai, Yachao Zhang, Jing Ning, Chunfu Zhang, Xiaojuan Sun, Zhitai Jia, Jincheng Zhang, Yue Hao
Abstract
Pure phase ε-(AlGa)2O3 films were deposited utilizing pulsed laser deposition (PLD) on a sapphire (0001) substrate under the assistance of tin element. High resolution X-ray diffraction (HRXRD) reveals the presence of out-of-plane compressive strain in ε-(AlGa)2O3 films. From XPS and TEM measurements, an increase in oxygen pressure causes a reduction in Al content and a rise in the film growth rate. Moreover, the ε-(AlGa)2O3 films achieve a wider bandgap with a decrease in oxygen pressure, determined by the transmittance spectra and responsivity. For oxygen pressure increasing from 0.006mbar to 0.01mbar and 0.03mbar, the responsivity of the MSM photodetectors are 0.86A/W, 1.87A/W, and 4.38A/W, and an external quantum efficiency (EQE) of 448%, 946%, and 2114%, respectively, indicating larger gains in ε-(AlGa)2O3 devices.