Defects and doping in GaN

First-principles calculations for defects and impurities in GaN provide a wealth of information about doping and electronic properties. We have been able to show that nitrogen vacancies are not the cause of n-type conductivity in GaN. Results for silicon and oxygen indicate that unintentional incorporation of these impurities is the most plausible explanation for n-type conductivity. For p-type GaN, we nd that Mg incorporation is limited by solubility. The role of hydrogen in acceptor-doped material is discussed.