Fibrous Al-Doped ZnO Thin Film Ultraviolet Photodetectors With Improved Responsivity and Speed

Abstract

Ultraviolet (UV) detection properties of undoped ZnO and Al-doped ZnO (AZO) based interdigitated metal-semiconductor-metal (MSM) structure are investigated in this paper. High quality of fibrous Al-doped ZnO thin films with enhanced conductivity and optical response with controlled doping of Al are synthesized using low-cost sol-gel method. The surface morphology and absorption properties of the films have been investigated. The responsivity and detectivity characteristics of both the devices are compared over 300–700 nm wavelengths. The Al-doped ZnO based Ag/AZO/Ag MSM structure show the maximum responsivity and detectivity of ~5.63 A/W and $\sim 1.8\times 10 ^{12}$ cmHz1/2W−1 while the respective values for the Ag/undoped-ZnO/Ag photodetector are ~3.65 A/W and $\sim 1.3\times 10 ^{12}$ cmHz1/2W−1 at 365 nm and $34~\mu \text{W}$ /cm2 incident UV intensity. The proposed AZO based MSM photodetector has smaller rise time (~30 s) than that (~35 s) of the undoped ZnO based MSM photodetector. However, the AZO based device shows slightly poor spectrum selectivity over the undoped ZnO based device.