Abstract
A peculiar mechanism of light absorption and emission related to the 3d-electron states in iron group atoms occurs in the dilute magnetic semiconductors (DMSs) along with the conventional band-to-band mechanism. The light emission from 3d-levels is important for electroluminescence applications. We have studied DMS Cd 1− x Mn x Te and Cd 1− x− y Mn x Mg y Te wherein the bright 3d-luminescence band near 2 eV is observed for ( x+ y)>0.4. A saturation of 3d-luminescence intensity J L is found to occur at a low excitation level J ex when only a minor portion of manganese ions is excited. The saturation of the 3d -luminescence is more readily achieved in Cd 1− x Mn x Te for x>0.5 when the temperature rises from 4 up to 77 K. The energy position of 3d-luminescence band in Cd 1− x− y Mn x Mg y Te depends weakly on the Mn and Cd relative concentrations, the value of y being fixed, but it shifts significantly towards higher energy with increasing value of y. Thus the incorporation of Mg contributes strongly to the inhomogeneous broadening and suppresses a Frenkel exciton migration via Mn 2+ ions. This result is consistent with the decrease of saturation for Cd 1− x− y Mn x Mg y Te as compared to Cd 1− x Mn x Te. The luminescence decay becomes faster with the increasing J ex due to the initiation of the nonradiative relaxation. The temperature and concentration dependences of J L point out the importance of energy transfer between Mn 2+ ions. The luminescence decay becomes faster with the increasing J ex due to the initiation of the nonradiative relaxation. It turns out that for Cd 0.6Mn 0.4Te wherein the 3d-luminescence excitation threshold coincides with band-to-band Wannier exciton energy, the dependence of the 3d-luminescence intensity upon J ex shows a peculiarity.
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