First-Principles Studies For Cu-Doped GaN

Diluted magnetic semiconductors (DMSs) have a broad application prospects as a crucial material for spintronics, because they can utilize both the charge and the spin of electrons simultaneously. However, the main problems of DMS are to analyse the mechanism of magnetism in these semiconductors and seek the DMS materials with high Curie temperature. The wide-band gap semiconductor GaN is a promising dilute magnetic semiconductor materials. In this paper, the electronic band structures and density of states of the Cu-doped GaN were calculated by using the first principles method based on density functional theory (DFT). Meanwhile, the origin of the magnetism was analysed. As a result, the magnetization and the Curie temperature of the Cu-doped GaN were investigated by using the theoretical scheme combining the first-principles calculations and the static mean-field theory. The main results of the paper are as follows.Firstly, we calculated the magnetization distribution in Cu-doped GaN by adopting the first principles method based on density functional theory. The results showed that a ferromagnetic coupling among Cu and N atom leads to a remarked ferromagnetism of the system. The origin of magnetism was analysed according to the electronic band structures and density of states of (Ga1-xCux)N (x=6.25%), and is mainly attributed to the interaction between Cu-d electron and nearest N-p electron. The 3d shell of the Cu is only partly occupied. As a result, there is a net magnetic moment in the Cu dopant.Secondly, the sp-d interaction between hole carrier and Cu-3d,together with direct Cu-Cu interaction,were investigated in Cu-doped GaN based on the theoretical scheme combining the first-principles calculations and the static mean-field theory. Then, the temperature-dependent magnetization in Cu-doped GaN was investigated. The Curie temperature (Tc) of this dilute magnetic semiconductor is obtained as a function of the Cu dopant concentration and the hole carrier density. It is demonstrated that nonmagnetic Cu doped GaN can be of room-temperature ferromagnetism. The results are in good agreement with experimental observations and indicate that ferromagnetism in this systems is tunable by controlling the Cu concentration and the hole density.As a result, it is predicted that room-temperature ferromagnetism can be achieved in Cu-doped GaN based on the first-principles calculations. The ferromagnetism is related to the dopant concentration and the hole density, and Curie temperature can be improved by controlling the Cu concentration and the hole density.