Fabry–Pérot interference-enhanced GaSe visible-blind UV photodetectors

Abstract

In this letter, we report the fabrication of an asymmetric Fabry–Pérot (F–P) structure by planar stacking of a GaSe nanosheet, Al₂O₃ spacer and Al back reflector. For selective absorption enhancement in UV region, the Al₂O₃ thickness was optimized to be 91 nm by the finite-difference time-domain (FDTD) solution. Compared with the device without the asymmetric F–P structure, the responsivity (R) and photoconductive gain (G) of the device were improved by one order of magnitude, giving a highest response at 265 nm illumination and the values of 1.08 A W⁻¹ and 5.05 at the weak light intensity of 20 μW cm⁻², respectively. The UV-to-visible rejection ratio (R₂₆₅/R₄₃₀) was also improved from 2.7 to 10.9, revealing the wavelength-selective absorption enhancement in the UV region. This work offers a promising strategy for high-performance UV photodetectors with potential applications in the new-generation market for miniaturized, bendable, and wearable devices.