INFLUENCE OF THE NEGATIVE THERMAL-EXPANSION COEFFICIENT ON THE LUMINESCENCE PROPERTIES OF (CDMNMG)TE

In zinc-blende II-VI alloys the thermal-expansion coefficient for low temperatures is negative and becomes positive at higher temperatures. We investigated the luminescence properties of molecular-beam-epitaxy- grown (CdMnMg)Te layers in the temperature range from 2 up to 200 K an d show that the anomalous temperature dependence of the lattice consta nt is reflected in the luminescence properties of the excitonic recomb ination and the internal transition of manganese (ITM). The temperatur e behavior of the ITM energy is nonmonotonic and the existence of a mi nimum in the photon energy (at the temperature T-Mn) can be correlated to the change of sign of the thermal-expansion coefficient. The decay constants of the ITM begins to decrease drastically at T-Mn, too. Con sidering a lattice constant dependent energy transfer rate to the infr ared emitting state (1.2 eV) of the manganese ion the variation of the lifetimes can also be explained by the temperature dependence of the lattice constant. Furthermore, we have measured the ITM in bulk layers and observed a different dependence of the ITM properties on the temp erature, demonstrating the influence of the growing conditions on the microscopic surrounding of the manganese ions. (C) 1996 American Insti tute of Physics.