Journal Article Vacancy-type defects in Mg-doped GaN grown by ammonia-based molecular beam epitaxy probed using a monoenergetic positron beam

Uedono, Akira  ,  Malinverni, Marco  ,  Martin, Denis  ,  Okumura, Hironori  ,  Ishibashi, Shoji  ,  Grandjean, Nicolas

119 ( 24 )  , p.245702 , 2016-06 , American Institute of Physics
Vacancy-type defects in Mg-doped GaN were probed using a monoenergetic positron beam. GaN films with a thickness of 0.5–0.7 μm were grown on GaN/sapphire templates using ammonia-based molecular beam epitaxy and characterized by measuring Doppler broadening spectra. Although no vacancies were detected in samples with a Mg concentration [Mg] below 7 × 1019 cm−3, vacancy-type defects were introduced starting at above [Mg] = 1 × 1020 cm−3. The major defect species was identified as a complex between Ga vacancy (V Ga) and multiple nitrogen vacancies (V Ns). The introduction of vacancy complexes was found to correlate with a decrease in the net acceptor concentration, suggesting that the defect introduction is closely related to the carrier compensation. We also investigated Mg-doped GaN layers grown using In as the surfactant. The formation of vacancy complexes was suppressed in the subsurface region (≤80 nm). The observed depth distribution of defects was attributed to the thermal instability of the defects, which resulted in the introduction of vacancy complexes during the deposition process.

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