Vacancy defects in O-doped GaN grown by molecular-beam epitaxy: The role of growth polarity and stoichiometry

Rummukainen, M.; Olla, J.; Laakso, A.; Saarinen, K.; Ptak, A. J.; Myers, T. H.
June 2004
Applied Physics Letters;6/14/2004, Vol. 84 Issue 24, p4887
Academic Journal
Positron annihilation spectroscopy is used to study vacancy defects in GaN grown by molecular-beam epitaxy due to different polar directions and varying stoichiometry conditions during oxygen doping. We show that Ga-polar material is free of compensating Ga vacancies up to [O]=1018 cm-3 in Ga stable growth, but high concentrations of VGa are formed in N-stable conditions. We also show that vacancy clusters are formed in N-polar material grown in Ga stable conditions, which may be related to the higher reactivity of the N-polar surface. These clusters have no apparent influence on the electrical properties of the material. We thus infer that their charge state is neutral. © 2004 American Institute of Physics.


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