Enhancement of TC by a carrier codoping method with size compensation for nitride-based ferromagnetic dilute magnetic semiconductors

Based on ab initio calculations of electronic structures of Mn-doped GaN, a carrier codoping method with size compensation to enhance the Curie temperature (TC) of GaN-based dilute magnetic semiconductors is proposed. Beryllium (Be) is chosen as a codopant to reduce the volume expansion caused by Mn doping, and also to enhance the 3d-density of states at Fermi level by hole doping. It is found that the mid-gap impurity band is strongly broadened due to strong p-d hybridization, resulting in a considerable increase of the hole density. With Be substituting both the cations and anions, the reduction of the antiferromagnetic super-exchange interaction in the regime of high Mn-concentrations and the highest value of TC due to the ferromagnetic double exchange interaction are strongly expected