Temperature dependence of the band gap energy of crystalline CdTe

In this paper we report the band gap energy value in CdTe single crystals by measuring the free exciton energy in the photoluminescence spectra taken at different temperatures and for two laser light intensities. The results have been analyzed using the Manoogian-WooIey (M-W) equation; by comparing them with the expression proposed by Vina; and using Varshni's expression for temperature variation of the band gap energy. The best fit was obtained with the M-W equation, and in relation with the UTs term in this equation, our analysis showed an s-value close to the unity, as has been reported for other materials. The value of U was very close to the theoretical prediction involving the product of the thermal expansion coefficient and the deformation potential of the material. From the term related to the electron-phonon interaction, we obtained a Debye temperature close to the tabulated value. Fitting the experimental data to the theoretical expression for E-g(T), the band gap energy for a temperature of 4.2 K was calculated to be 1.6065 eV in agreement with the well-established value for this material; a band gap energy of 1.5125 eV is proposed for a temperature of 300 K. (C) 2000 Elsevier Science Ltd. All rights reserved.