Effect of growth polarity on vacancy defect and impurity incorporation in dislocation-free GaN

We have used positron annihilation, secondary ion mass spectrometry, and photoluminescence to study the point defects in GaN grown by hydride vapor phase epitaxy (HVPE) on GaN bulk crystals. The results show that N polar growth incorporates many more donor and acceptor type impurities and also Ga vacancies. Vacancy clusters with a positron lifetime τ D = 470 ± 50 ps were found near the N polar surfaces of both the HVPE GaN layers and bulk crystals.