Vacancy-type defects in AlN grown by metal-organic vapour phase epitaxy

(MOVPE) and lateral epitaxial overgrowth (LEO) using halide vapour phase

epitaxy were probed by a mono-energetic positron beam. Doppler broadening

spectra of the annihilation radiation were measured and compared to the spectra

calculated using the projector augmented-wave method. For MOVPE-AlN, the

concentration of vacancy-type defects was high near the interface between AlN and

the GaN buffer layer, and the defect-rich region expanded from the interface towards the surface when the NH3 flow rate increased. For the sample grown on

the AlN buffer layer, however, the introduction of such defects was suppressed.

For LEO-AlN, distinct deep emission peaks at 3–6eV were observed in

cathodoluminescence spectra. From a comparison between Doppler broadening

spectra measured for LEO-AlN and computer simulated ones, an origin of the

peaks was identified as complexes of Al vacancy (VAl) and oxygen atoms

substituting nitrogen sites such as VAl(ON)n (n = 3 or 4).

Vacancy-Oxygen Complexes and Their Optical Properties in AlN Epitaxial Films

Studied by Positron Annihilation. A.Uedono, S.Ishibashi, S.Keller, C.Moe,

P.Cantu, T.M.Katona, D.S.Kamber, Y.Wu, E.Letts, S.A.Newman, S.Nakamura,

J.S.Speck, U.K.Mishra, S.P.DenBaars, T.Onuma, S.F.Chichibu: Journal of Applied

Physics, 2009, 105[5], 054501