Cooperative quenching of intra-center luminescence in Cd1-xMnxTe under high density excitation

Abstract

Intra-center luminescence transients of 2 eV-band in Cd0.25Mn0.75Te thin film and Cd0.6Mn0.4Te /Cd0.5Mg0.5Te multi quantum wells under strong excitation were investigated both experimentally and by Monte-Carlo simulation at temperature 77 K. Sharp fall at initial time span in the experimental transients is described by Monte Carlo model, in which Mn2+-ion excitations interact with each other through dipole-dipole form. Good conformity of calculated and experimental data proved importance of far-field form of the interaction. Calculations showed that elemental act of the interaction includes a quenching of one excitation, the other one being instantaneously up-converted and returned to initial state with high probability. Initial quenching rate is more than two orders of magnitude higher than that of the luminescence emission. The quenching is assisted by energy transfer. Saturation of Mn2+-ion system is calculated to be weak. A value of the quenching coefficient is 2.5×10−13 cm3 s−1, which is as high as that of some regular crystals. Experimental transients of the hetero structures showed a reduction of the quenching at narrower quantum wells. Calculations proved the initial peak diminished and narrowed if the well width was decreased. The tendency may be helpful to estimate contribution of morphological changes in transient short constituent at decrease of a nanostructure dimension. The model can be extended for other semi magnetic semiconductors of II-VI group with isoelectronic substitution by ions of iron group.