Impurity-semiconductor band hybridization effects on the critical temperature of diluted magnetic semiconductors

We have studied the critical temperature of diluted magnetic semiconductors by means of Monte Carlo simulations and coherent-potential-approximation (CPA) calculations. In our model for this system, the magnetic ions couple with the carriers through an antiferromagnetic exchange interaction J and an electrostatic interaction W. The effective impurity potential $J-W$ controls the hybridization between the magnetic impurities and the hole charge on the dopants. We find that the critical temperature depends substantially on the hole charge on the magnetic impurities. The CPA critical temperature is always lower than that obtained in the Monte Carlo simulations, although all trends in the simulation results are reproduced in the CPA calculations. Finally we predict the existence of pockets of phase segregation instability close to the carrier’s band edges.