Optical absorption studies inCd1−xMnxSe

Optical absorption results on single-crystal samples of ${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$Se are presented. Data were taken over the range 1.5–2.5 eV. Measurements were made at 300 and 195 K, liquid-nitrogen, and liquid-helium temperatures on samples with nominal manganese concentrations x=0.30, 0.42, and 0.45. Dichroism associated with the fundamental edge was found for all x and T studied. Onset of a strong absorption below the intrinsic edge is seen at ∼2.3 eV in high-x material; this feature is associated with excitation of a 2.13-eV emission band and is therefore identified as the threshold of the ${}_{}{}^6{}_{}{}^{}\mathrm{A}_1^{}{}_{}{}^{}$(${\mathrm{}}^6$S)→${\mathrm{}}^4$ ${\mathrm{T}}_1$( ${}_{}{}^4{}_{}{}^{})$ transition of ${\mathrm{Mn}}^{2+}$ in the 3$d^5$ configuration. We report an additional absorption feature of the order α∼1 ${\mathrm{cm}}^{\mathrm{-}1}$ extending from 2.3 to ∼1.5 eV; we associate this feature in part with the excitation of a 1.35-eV emission band discussed earlier in the literature. The band-edge dichroism, taken as a measure of the crystal-field splitting, is found to decrease with increasing x, as reported in earlier electroreflectance results. In contrast with the electroreflectance data, however, a strong temperature dependence of the dichroism occurs near the upper limit (x∼0.45) of the single-phase wurtzite region. Possible mechanisms for this result are discussed.