ABSOLUTE ABSORPTION-COEFFICIENT OF CD1-0.09MN0.09TE, CD1-0.16MN0.16TE, CD1-0.34MN0.34TE NEAR THE E0 GAP IN EXTERNAL MAGNETIC-FIELDS

The optical absorption coefficient of Cd1-xMnxTe (x=0.09, 0.16, 0.34) is determined near the E0 gap at T=1 K in external magnetic fields up to 5 T. Single-crystal Cd1-xMn xTe layers with thicknesses 1-2 mu m were grown on a (001) GaAs substrate by MBE. The substrate was removed by mechanical polishing and chemical etching. In Cd1-xMnxTe a large splitting of the twofold degenerate Gamma 6 conduction band and the fourfold degenerate Gamma 8 valence band occurs at low temperatures in external magnetic fields. As a consequence the free exciton ground state splits into six components. In the Faraday configuration two allowed optical transitions for both right-and left-circular polarized light can be observed in the absorption spectrum. The measured splitting of the exciton ground-state energy as a function of the magnetic field is in good agreement with an existing theoretical band model for diluted magnetic semiconductors. Without an external magnetic field the authors obtain for the absorption coefficient a value of 4.0*104 cm-1 for the continuum exciton states near E0.