Doping Properties of Amphoteric C, Si, and Ge Impurities in GaN and AlN

Electronic structure of substitutional group-IV impurities C, Si, and Ge in hexagonal GaN and AlN were studied by quantum molecular dynamics. C$\text{}_{N}$ is a very shallow acceptor, and thus a promising p-type dopant. Both Si and Ge are excellent donors in GaN. However, in AlGaN alloys the DX configurations are stable for a sufficiently high Al content, which quenches the doping efficiency. Electronic structure of nearest-neighbor X$\text{}_{cation}$-X$\text{}_{N}$ pairs is also discussed.