Excitonic energy transfer to the 3d electrons of Mn2+ in Cd1-xMnxTe

We studied the energy transfer between excitons and the 3d electrons of Mn2+ in Cd1-xMnxTe crystals within a Mn concentration range of 0.2 less than or equal to x less than or equal to 0.45 at T=2, 5, and 20 K by emission, excitation, and time-resolved photoluminescence measurements. Time integrated emission spectra show a strong quenching of the L(2)-type exciton luminescence together with a strong increase of intensity of the T-4(1)(G)-->(6)A(1)(S)Mn2+ luminescence if the Mn concentration is raised from x=0.32 to 0.43. Excitation spectra of the T-4(1)(G)-->(6)A(1)(S) Mn2+ luminescence give evidence of an excitonic energy transfer via free and intrinsically localized excitons to the 3d shell of Mn2+. By time-resolved photoluminescence measurements we investigated the lapse of luminescence at discrete energies in the exciton luminescence band using pulsed band-to-band excitation. The luminescence shows a nearly exponential decay. We see a strong decrease of the luminescence decay time when the Mn2+ ions act like energy absorbers for the exciton energies.