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 β-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 introduction of MLG with both high electrical conductance and UV transmittance greatly enhances 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 exhibits 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 (τr = 2 ms, τd = 8.8 ms), and exhibits a maximum responsivity of 9.2 mA/W and detectivity of 5.27 × 1011 Jones under 230 nm-light illumination, 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.