Epitaxial growth of ε-(AlGa)2O3 films on sapphire substrate by PLD and the fabrication of photodetectors

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.