INVESTIGATIONS ON OPTOELECTRONIC PROPERTIES OF DC REACTIVE MAGNETRON SPUTTERED CdTe THIN FILMS

In the present work two individual metallic targets of Cd and Te were used for the deposition of CdTe thin films on mica substrates from room temperature to 300 degrees C by DC reactive magnetron sputtering method. XRD patterns of CdTe exhibit peaks at 2 theta = 27.7 degrees, 36. 2 degrees and 45.1 degrees, which corresponds to reflection on (2 0 0), (2 2 0) and (3 1 1) planes of CdTe cubic structure, respectively. The conductivity of CdTe thin films measured from four probe method decreases with the increase of substrate temperature. The activation energies (Delta E) of CdTe thin films are also found to be decrease with the increase of substrate temperature. These results may be correlated with Te excess that is greater in respective CdTe films. Optical transmittance spectra of CdTe thin films have a clear interference pattern in the longer wavelength region. The films have good transparency (T > 85 %) exhibiting interference pattern in the spectral region between 1200 - 2500 nm. The optical band gap of CdTe thin films are found to be in the range of 1.48 - 1.57 eV. The refractive index, n decreases with the increase of wavelength, lambda. The value of n and k increases with the increase of substrate temperature.