High gain GaN ultraviolet Schottky photodetector with Al-doped ZnO interlayer

We fabricated an GaN Schottky photodiode (PD) with Al-doped ZnO (AZO) interlayer for ultraviolet (UV) photodetection, and its optoelectrical properties with a comparison to the GaN Schottky PD without AZO interlayer. The AZO-interlayered GaN Schottky PD was highly sensitive to 350 nm laser irradiation, having a photoresponsivity of 11.1 AW^–1 and detectivity of 1.04 × 10¹² cm·Hz^1/2·W^–1 at -2 V as against 0.28 AW⁻¹ and 2.23 × 10¹⁰ cm·Hz^1/2·W^–1 for the GaN Schottky PD without AZO interlayer. The transient photoresponse revealed a rise and decay time of 203 and 293 ms, respectively for the AZO-interlayered GaN Schottky PD. The introduction of AZO interlayer resulted in a reduction in the noise spectral density, leading to an increase in the detectivity by more than an order, as compared to GaN Schottky PD without AZO interlayer. An improved photodetection behavior of the AZO-interlayered GaN Schottky PD could be ascribed to effective GaN surface passivation and reduction of the surface states by the AZO interlayer. The utilization of the AZO in GaN-based UV photodetectors can provide a potential and simplistic approach towards the fabrication of high performance GaN-based UV photodetectors.