Effect of sputter pressure on UV photodetector performance of WO3 thin films

Abstract

Tungsten trioxide (WO3) is a promising material for ultra-violet (UV) photodetector applications. In this research, high sensitivity and external quantum efficiency (EQE) of UV photodetector test-device is fabricated by the deposition of WO3 films through sputtering at 10 mTorr sputter pressure. The effect of sputter pressure on the crystallinity and morphology as well as the photodetector performance of WO3 films is studied. Here, the thickness of the WO3 films is decreased from 225 nm to 95 nm as the sputter pressure is increased from 10 mTorr to 20 mTorr due to the low deposition rate upon accumulation of argon ions. The crystallinity and surface roughness are found to be high for WO3 film deposited at 10 mTorr as an effect of Ostwald ripening. The SiO2 layer on Si substrates acts as a passivation to inhibit the surface recombination and the ohmic-contact between WO3 and Ti electrode is helped to enhance the photocurrent. The higher crystallinity, tailored grain size, and surface roughness of WO3 films assist to achieve high responsivity and EQE by minimizing the overall impedance. Therefore, WO3 films deposited at 10 mTorr sputter pressure is suitable for UV photodetector applications with good stability and higher photodetector performance.