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

In this article, we demonstrate beta-Ga2O3 and SnO2 mixed-phase thin films with dominant ((2) over bar 01)-beta-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) over bar 01)-beta-Ga2O3/c-Al2O3 (similar to 3%) and (200)-SnO2/c-Al2O3 (similar to 0.6%). Therefore, we also successfully demonstrate preferred-orientation ((2) over bar 01)-beta-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. (c) 2020 Elsevier B.V. All rights reserved.

Automated summary

This article demonstrates the preparation of beta-Ga2O3 and SnO2 mixed-phase thin films with specific orientations on c-face sapphire by chemical vapor deposition, showing improved photoelectric properties in photodetectors with more SnO2 content. By controlling the ratios of Sn and Ga in precursors, preferred orientations are achieved, leading to better performance compared to pure and mixed-phase Ga2O3-based photodetectors.