Thermal and Optical Properties of Zn1−x Mn x Te Diluted Magnetic Semiconductor Studied by Photoacoustic Spectroscopic Method

Abstract

Using photoacoustic spectroscopy, the composition-dependent absorption coefficient (α), thermal diffusivity (σ), and optical bandgap (Eg) of Zn1−xMnxTe diluted magnetic semiconductor have been measured. For higher Mn compositions, the absorption spectrum of the Zn–Mn–Te system consists of three regions, viz., the high absorption region, the exponential region, and the weak absorption tail. The bandgap follows a nonlinear variation with composition, showing a downward bowing with a minimum around x = 0.31 as a consequence of the electro-negativity difference between the substituted atoms. The composition-dependent band-edge effective mass of the carriers does not show the bowing behavior indicating that the momentum matrix is not the same for all the Zn1−xMnxTe alloys due to different lattice constants. The absorption spectra show that the transition is allowed and direct.