Thermal and Optical Properties of Zn_(1-x)Mn_xTe Diluted Magnetic Semiconductor Studied by Photoacoustic Spectroscopic Method

摘要

Using photoacoustic spectroscopy, the composition-dependent absorption coefficient (α), thermal diffusivity (σ), and optical bandgap (E_g) of Zn_(1-x)Mn_xTe 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 band-gap 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 Zn_(1-x)Mn_xTe alloys due to different lattice constants. The absorption spectra show that the transition is allowed and direct.