Temperature dependence of the band-edge photoluminescence of Zn1−xMnxSe films

Abstract

We report a systematic investigation of band-edge photoluminescence of the diluted magnetic semiconductor alloy Zn1-xMnxSe for a series of compositions (0 < x < 0.485). The specimens investigated were in the form of thin films fabricated by molecular beam epitaxy. The near band-edge emissions of donor-bound excitons (designated as I-2) and of neutral acceptor-bound excitons (I-1) were systematically investigated as a function of temperature and of alloy composition. These measurements also allowed us to determine the LO-phonon energy (h) over bar omega(LO) = 31.2 +/- 0.2 meV From the temperature dependence of the bound exciton peak, the Varshni temperature parameter alpha was found to increase linearly with increasing Mn concentration x, while beta decreased with x. From the temperature dependence of the full width at half maximum (FWHM) of the I-2 emission line, the broadening factors Gamma (T) were determined from the fit to the data. For x > 0.20 the effect of inhomogeneous broadening Gamma(inh) on Gamma(T) was found to be stronger than that of the longitudinal optical phonon term Gamma(LO). Furthermore, the activation energies of thermal quenching were obtained for both the I-2 and the I-1 peaks from the temperature dependence of the bound exciton peaks, and were found to decrease with increasing Mn concentration. Finally, we show that at high temperature the broadening of the FWHM is dominated by the LO-phonon interaction.