This work studies Ga vacancies in a GaN epitaxial layer using a rarely accessible method: variable energy positron annihilation spectroscopy. This work provides unique insights into how technological MOVPE parameters (temperature, carrier gas and precursor types) influence Ga vacancy formation. Correlating photoluminescence results with VGa concentration, as determined by VEPAS, suggests that yellow band luminescence in GaN is likely unconnected with VGa. Additionally, increased VGa concentration enhances excitonic luminescence. One possible explanation is that Ga vacancies are inefficient recombination centers, and that VGa prevents the formation of other highly efficient non-radiative defects. The possible types of these defects are suggested.
