Influence of layer thickness on the formation of In vacancies in InN grown by molecular beam epitaxy

We have used a low-energy positron beam to identify In vacancies in InN layers grown on $Al2O3$ by molecular beam epitaxy. Their concentration decreases from $∼5×1018$ to below $1016 cm−3$ with increasing layer thickness (120–800 nm). The decrease in the vacancy concentration coincides with the increase in the electron Hall mobility, suggesting that In vacancies act as electron scattering centers.