Preparation and characteristics of the In-doped ZnO thin films and the n-ZnO:In/p-Si heterojunctions for optoelectronic switch

Abstract

n-ZnO:In/p-Si heterojunctions have been fabricated by sputter deposition of n-ZnO:In on p-Si substrates. The lowest resistivity n-ZnO:In film was obtained at a substrate temperature of 150$^o$C using a ZnO target doped with 2 wt\% In$_2$O$_3$. At substrate temperature above 300$^o$C the resistivity of the film increases as the carrier concentration decreases . This implies a significant decrease in the donor impurity, which is ascribed to evaporation of the indium during film growth. The wavelength dependent properties of the photo-response for the heterojunction were investigated in detail by studying the effect of light illumination on current - voltage (I-V) characteristic, photocurrent spectra at room temperature. From the photocurrent spectra, it was observed that the visible photons are absorbed in the p-Si layer %and under reverse bias conditions , while ultraviolet (UV) photons are absorbed in the depleted n-ZnO:In film under reverse bias conditions. %These results indicated that The properties of ZnO:In films prepared by r.f. magnetron sputtering are good enough to be used in photoelectrical devices.