Strong acceptor density and temperature dependences of thermal activation energy of acceptors in a Mg-doped GaN epilayer grown by metalorganic chemical-vapor deposition

P-type GaN layers were grown on sapphire by metalorganic chemical-vapor deposition and then rapid thermal annealing (RTA) was performed to electrically activate Mg impurities. Varied acceptor densities were obtained by RTA temperature and Mg concentration. Temperature-dependent Hall effects show that the thermal activation energy of the acceptor (EA) is strongly dependent on the acceptor density (NA), approximated by EA(0)=372−1.16×10−18 NA meV at 0 K. A strong temperature dependence of EA was also obtained in this study.