Fabrication and optical-electrical characteristics of ZnS/ZnO films by pulsed laser deposition

Abstract

Zinc sulfide/Zinc oxide (ZnS/ZnO) films were prepared on silicon (Si) wafers at different temperatures via pulsed laser deposition, and the structure, morphology and optical characteristics were investigated. As the growth temperature increases, the crystallization quality of ZnS and ZnO films improves, and the surface morphology of ZnS/ZnO films becomes more uniform and dense, accompanied by grain growth. Photoluminescence spectra of ZnS/ZnO films show that there are two emission peaks located at about 380 and 500 nm. With the increase of growth temperature, the luminescence intensity of the two peaks increases first and then decreases, and the reduction of ultraviolet luminescence is more obvious, accompanied by the blueshift of the peak position. ZnS films have played a major role in the green luminescence of ZnS/ZnO films. The average transmittance of ZnS/ZnO films is about 75% in the visible light region. With the increase of growth temperature, the transmittance increases gradually, accompanied by the absorption edge moving towards the short wavelength. Current-voltage characteristics of ZnS/ZnO/Si heterojunctions show similar rectifying behavior with common p-n junction diodes. This indicates that ZnS/ZnO films have potential applications in optoelectronic devices.