A COMPARISON OF THE PHYSICAL-PROPERTIES OF CDTE SINGLE-CRYSTAL AND THIN-FILM

Measurements of optical absorption and photoconductivity (steady state , frequency dependent, time dependent) were made on an n-type CdTe sin gle crystal and on an evaporated CdTe thin film. For the single crysta l the standard steady state photoconductivity showed an intrinsic peak at 1.4 eV. The lifetime calculated from ac photoconductivity measurem ents was in the range (1.1-5) x10(-2) s. The lifetime showed a minimum at exactly the same photon energy at which the photocurrent was maxim um. The decay time was always longer than the lifetime. Optical absorp tion measurements revealed a direct transition and an optical gap of 1 .47 eV at 80 K. Polycrystalline thin films of CdTe were grown by vacuu m evaporation on glass substrates held at 90 degrees C. The films show ed a peak in the spectral distribution (l(ph)-lambda) curve at 1.65 eV . Direct and indirect transitions were again observed and found to be temperature dependent.