P-type activation study on Mg-doped GaN films prepared by metalorganic vapor phase epitaxy

The annealing behaviors of Mg-doped GaN films were investigated by Hall measurement and extended X-ray absorption fine structure (EXAFS) spectroscopy. We have found that under the experimental set-up employed here, a better p-type film quality can be obtained at 700 °C for 45 min., at which the resistivity can be reduced to approximately 0.2 Ω-cm and hole concentration can be increased significantly to approximately 3×10 ¹⁸ cm ^-3 . Moreover, EXAFS measurement strongly suggests that undesirable donor energy levels, most likely N vacancies, may appear simultaneously in the solid during the Mg doping. This feature is believed of be one of the essential factors responsible for the high compensation, hence poor Hall properties in p-type GaN sample.