A low-energy positron beam was used to identify In vacancies in InN layers grown on Al2O3 by molecular beam epitaxy. Their concentration decreases from about 5 x 1018 to below 1016/cm3 with increasing layer thickness (120 to 800nm). The decrease in the vacancy concentration coincides with the increase in the electron Hall mobility, suggesting that In vacancies act as electron scattering centers.

Influence of Layer Thickness on the Formation of In Vacancies in InN Grown by Molecular Beam Epitaxy. J.Oila, A.Kemppinen, A.Laakso, K.Saarinen, W.Egger, L.Liszkay, P.Sperr, H.Lu, W.J.Schaff: Applied Physics Letters, 2004, 84[9], 1486-8