Positron annihilation spectroscopy was used to study the thermal behavior of various native vacancy defects typical of freestanding GaN grown by hydride vapor phase epitaxy under high pressure annealing at different annealing temperatures. The results showed that the VGa-ON pairs dissociate and the Ga vacancies anneal out from the bulk of the material at 1500 to 1700K. A binding energy of Eb=1.6eV could be determined for the pair. Thermal formation of Ga vacancies was observed at annealing temperatures above 1700K, indicating that Ga vacancies were created thermally at the high growth temperature, but their ability to form complexes such as VGa-ON determines the fraction of vacancy defects surviving the cooling down. The formation energy of the isolated Ga vacancy was experimentally determined.

Thermal Stability of In-Grown Vacancy Defects in GaN Grown by Hydride Vapor Phase Epitaxy. F.Tuomisto, K.Saarinen, T.Paskova, B.Monemar, M.Bockowski, T.Suski: Journal of Applied Physics, 2006, 99[6], 066105 (3pp)