High-performance Ga2O3/FTO-based self-driven solar-blind UV photodetector with thickness-optimized graphene top electrode

Self-driven solar-blind ultraviolet photodetectors (SBUVPDs) have attracted considerable interest for their superior sensitivity and operation flexibility. Herein, we demonstrate realization of a simple vertical-structured self-driven SBUVPD by pulsed laser deposition of b-Ga2O3 thin film on commercially available fluorine doped tin oxide (FTO) substrate, adopting multi-layer graphene (MLG) as the top electrode. On the one hand, the intro-duction of MLG with both high electrical conductance and UV transmittance greatly en-hances photocurrent and responsivity of the photodetector. On the other hand, the dominating Schottky contact between Ga2O3 and MLG creates a net built-in electric field, leading to self-driven photoresponse of the device with improved response speed. With optimized thickness (8 +/- 2 single layers of graphene) of the top electrode, the device ex-hibits the best detection performance that is superior to most of previous reports towards UV illumination at 0 V bias. It delivers a photocurrent as high as 31 nA towards 250 nm-light with ultra-fast response speed (tr = 2 ms, td = 8.8 ms), and exhibits a maximum responsivity of 9.2 mA/W and detectivity of 5.27 x 1011 Jones under 230 nm-light illumi-nation, while the response cuts off at light wavelength of 261 nm, falling completely within the solar blind band. In addition, the device has good multi-cycle repeatability and stability, showing great application potential in solar-blind UV detection.(c) 2022 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).