Impurity–host interactions in Cr-substituted ZnSe

The physics of charge-transfer processes in semiconductors is a challenging and longstanding problem. Focusing on Cr-substituted ZnSe semiconductors, important for optoelectronic and spintronic devices, several processes and their energetics are analysed using first-principles. In contrast to the properties exhibited by deep gap levels, our results for highly Cr doped ZnSe show small variations in the equilibrium configurations, forces and electronic density around the Cr for different charge states. Therefore, the delocalization of the electronic charge between the impurity and host leads to a decrease of the effective Coulomb repulsion and becomes then the fundamental mechanism to inhibit nonradiative recombination via multiphonon emission for the modes studied.