Positron spectroscopy was used to study the formation of vacancy defects in undoped n-type metalorganic chemical vapor deposited samples of variable stoichiometry. It was found that Ga vacancies were present in all samples. Their concentration increased from 1016 to 1019/cm3 when the V/III molar ratio was increased from 1000 to 10000. Under N-rich conditions, Ga lattice sites were therefore left empty and abundant Ga vacancies were formed. The creation of Ga vacancies was accompanied by a decrease in the free electron concentration from 1020 to 1016/cm3; thus demonstrating their role as compensating centers.

Gallium Vacancies and the Growth Stoichiometry of GaN studied by Positron Annihilation Spectroscopy. K.Saarinen, P.Seppälä, J.Oila, P.Hautojärvi, C.Corbel, O.Briot, R.L.Aulombard: Applied Physics Letters, 1998, 73[22], 3253-5