Transport properties of photogenerated carriers in relaxation-case cadmium telluride films

The transport properties of photogenerated carriers in semi-insulating ($\rho ={10}^8-{10}^9$ Ω cm) polycrystalline films of CdTe are investigated. Measurements of the spectral variation of the optical-absorption coefficient and photomagnetoelectric short-circuit current are employed to obtain excess carrier diffusion lengths in films prepared at substrate temperatures of 150, 250, and 350 °C. Analysis of the data also yields values for an effective Hall mobility, which, with stated approximations, allows an estimate of the diffusion-length lifetime ${\tau }_0$. Excess carrier diffusion lengths and diffusion-length lifetimes are found to be extremely small and in general agreement with earlier predictions concerning the magnitude of these parameters in relaxation semiconductors.