Mixed-phase β-Ga2O3 and SnO2 metal-semiconductor-metal photodetectors with extended detection range from 293 nm to 330 nm

Abstract

In this article, we demonstrate β-Ga2O3 and SnO2 mixed-phase thin films with dominant (2¯01)-β-Ga2O3 and (200)-SnO2 orientations on c-face sapphire (c-Al2O3) by chemical vapor deposition in a tube furnace. Transmission electron microscopy (TEM) reveals their simultaneous growth on substrate due to the small mismatches of (2¯01)-β-Ga2O3/c-Al2O3 (∼3%) and (200)-SnO2/c-Al2O3 (∼0.6%). Therefore, we also successfully demonstrate preferred-orientation (2¯01)-β-Ga2O3 and (200)-SnO2 mixed-phase thin films by controlling the Sn and Ga ratios in precursors. At 40 V, the photoelectric properties of metal-semiconductor-metal (MSM) photodetectors are modulated with more SnO2 content in mixed-phase thin films, including the dark current from 11 pA to 4 nA, the peak response in UVC from 240 nm (2 mA/W) to 260 nm (1.15 A/W), the tunable cut-off wavelength from 274 nm to 297 nm, and the extended detection range at long wavelength from 293 nm to 330 nm. Our devices show Ga2O3-like photoresponse properties rather than SnO2-like properties with lower dark current, comparable responsivity and detectivity, and faster response time than the performances of parts of the pure and mixed-phase Ga2O3-based photodetectors with untunable detection rang, which is expected to extend wider applications of other Ga2O3-based mixed-phase materials during doping or alloying, and paves a new and feasible way to realize high-performance Ga2O3-based photodetectors with controllable detection range.