Effect of oxygen flow rate and radio-frequency power on the photoconductivity of highly ultraviolet sensitive ZnO thin films grown by magnetron sputtering

We have investigated the effect of oxygen flow rate and radio-frequency (RF) power on the photoconductivity properties of ZnO thin films grown by magnetron sputtering and correlated the changes to the structural qualities. The electrical measurements show that the carrier concentration decreases with increase in the oxygen flow rate which is attributed to the probable increase in the oxygen vacancy (VO)-related defects. The photocurrent spectra show that as the oxygen content increases, the films become lesser and more sensitive to the visible and ultraviolet (UV) lights respectively. As a result, the photo-to-dark current ratio (gain) increases to a value of 1.10 × 106. As the RF power increases from 50 W to 150 W, the films become more conducting. The photoconductivity results show that as the RF power increases, the UV gain decreases slowly indicating that highly UV sensitive films can be grown at lower RF power.