TiO2-Based Metal–Semiconductor–Metal Ultraviolet Photodetectors Deposited by Ultrasonic Spray Pyrolysis Technique

Abstract

This paper uses nonvacuum ultrasonic spray pyrolysis deposition method to grow TiO2 for ultraviolet (UV) detection. The analyses of the materials like X-ray photoelectron spectroscopy, X-ray diffraction, and photoluminescence were investigated. The 600 °C annealing temperature is the optimum condition to obtain the anatase TiO2. The metal–semiconductor–metal (MSM) photodetectors (PDs) with 3-, 5-, 7-, 10- $\mu \text{m}$ finger spacing were fabricated and the performance was investigated. The PD with 10- $\mu \text{m}$ finger spacing has the lowest dark current of $2.92\times 10^{-11}$ A and the highest UV-to-visible rejection ratio ( $R_{{{{\rm UV}/{\rm VIS}}}})$ of $2.1\times 10^{5}$ at 5 V. The PD with 5- $\mu \text{m}$ finger spacing has the lowest noise equivalent power of $2.57\times 10^{-9}$ W and the highest detectivity ( $D^\ast )$ of $5.46\times 10^{8}$ cmHz $^{0.5}\text{W}^{-1}$ . The rising time and the falling time of the PD are 5 and 12 s. In addition, the TiO2-based MSM PD in this paper operated normally at 450 K; however, the performance is slightly degraded. The mechanisms causing degradation at high temperature were investigated.