Study of the 2.0-eV photoluminescence band inCd1−xMnxTesemiconductor alloys

Abstract

The 2.0-eV photoluminescence band in ${\mathrm{Cd}}_{1-x}{\mathrm{Mn}}_x\mathrm{Te}$ semiconductor alloys is investigated over the range $0.4\le x\le 0.7$. The emission is ascribed to the ${}_{}{}^4{}_{}{}^{}T_1^{}{}_{}{}^{}\left({}_{}{}^4{}_{}{}^{}G\right)\to {}_{}{}^6{}_{}{}^{}A_1^{}{}_{}{}^{}\left({}_{}{}^6{}_{}{}^{}S\right)$ internal transition of ${\mathrm{Mn}}^{2+}$ within the $3d^5$ state. Excitation spectra reveal a drop in intensity near the fundamental edge; the decrease is a result of competitive intrinsic absorption that does not lead to ${\mathrm{Mn}}^{2+}$ emission. Onset of the ${}_{}{}^6{}_{}{}^{}A_1^{}{}_{}{}^{}\to {}_{}{}^4{}_{}{}^{}T_1^{}{}_{}{}^{}$ transition can be seen for $x>\mathrm{}0.4\mathrm{}$; excitation in samples with $x>\mathrm{}0.6\mathrm{}$ reveals the ${}_{}{}^6{}_{}{}^{}A_1^{}{}_{}{}^{}\to {}_{}{}^4{}_{}{}^{}T_2^{}{}_{}{}^{}$ transition as well. The strongly localized character of the emission is established from full width at half maximum data. A phonon energy of $\hslash \omega =53\mathrm{}\pm 16$ ${\mathrm{cm}}^{-1\mathrm{}}$ and a Huang-Rhys factor of $S=26\mathrm{}\pm 2$ is obtained with the use of a linear configurational coordinate model. In addition, a value of inhomogeneous broadening $H_{\mathrm{in}}=80\mathrm{}$ meV (645 ${\mathrm{cm}}^{-1\mathrm{}}$) is found from the analysis. Various sources of inhomogeneous broadening and line shift are discussed.