Nonlinear properties of intraionic luminescence of Mn2+ in dilute magneticsemiconductors CdMnTe and CdMnMgTe

A peculiar mechanism of light absorption and emission related to the 3d-ele ctron states in iron group atoms occurs in the dilute magnetic semiconducto rs (DMSs) along with the conventional band-to-band mechanism. The light emi ssion from 3d-levels is important for electroluminescence applications. We have studied DMS Cd1-xMnxTe and Cd1-x-yMnxMgyTe wherein the bright 3d-lumin escence band near 2 eV is observed for (x + y) > 0.4. A saturation of 3d-lu minescence 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 Cd1-xMnxTe for x > 0.5 when the temperature rises from 4 up to 77 K. The energy position of 3d-lumines cence band in Cd1-x-yMnxMgyTe depends weakly on the Mn and Cd relative conc entrations, the value of y being fixed, but it shifts significantly towards higher energy with increasing value of y. Thus the incorporation of Mg con tributes strongly to the inhomogeneous broadening and suppresses a Frenkel exciton migration via Mn2+ ions. This result is consistent with the decreas e of saturation for Cd1-x-yMnxMgyTe as compared to Cd1-xMnxTe. The luminesc ence decay becomes faster with the increasing J(ex) due to the initiation o f the nonradiative relaxation. The temperature and concentration dependence s of J(L) point out the importance of energy transfer between Mn2+ ions. Th e luminescence decay becomes faster with the increasing J(ex) due to the in itiation of the nonradiative relaxation. It turns out that for Cd0.6Mn0.4Te wherein the 3d-luminescence excitation threshold coincides with band-to-ba nd Wannier exciton energy, the dependence of the 3d-luminescence intensity upon J,, shows a peculiarity. (C) 2000 Elsevier Science B.V. All rights res erved.