Electrical and optical properties of rf-sputtered CdTe films

Abstract

In this paper some electrical and optical properties ofn-type CdTe films prepared by rf sputtering at 180 W power have been reported. For doping the films a number of pellets of pure Cd placed on the CdTe target were simultaneously sputtered with the target material to get Cd-doped CdTe films. The films after doping were foundn-type. Maximum doping concentration obtained this way was of the order of 10¹⁴ cm⁻³. XRF spectra of target material and the rf-sputtered films were found to be more or less similar. All the films were found to have large number of defects indicated by profound aging effect in the initial stages of aging. The films became stable for measurements after about 8–10 days. Activation energy and band gap found from the temperature dependence of dark conductivity were 0–5 eV and 1.43 eV respectively. Photoconductivity of the films was studied and the photoconductive rise time, decay time and the decay constants were determined from the photoconductive rise and decay curves at 500 Lx and 1000 Lx of intensity of illumination.