The nature of the yellow-band luminescence of GaN which had been grown onto sapphire, or patterned Si3N4, was investigated. The states which produced the levels that were responsible for the yellow-band luminescence and donor-acceptor emissions, arose from complexes which comprised extended defects and native point defects (probably Ga vacancies) or impurities (such as C). In the case of GaN which had been grown directly onto a GaN buffer layer, the yellow-band luminescence and donor-acceptor emissions could be eliminated simply by increasing the buffer-layer growth temperature. This enlarged the hexagonal crystallites and consequently reduced the density of the extended defects. In the case of laterally overgrown GaN, the much lower density of extended defects substantially suppressed the yellow-band luminescence emission.

Nature and Elimination of Yellow-Band Luminescent and Donor-Acceptor Emission of Undoped GaN. G.Li, S.J.Chua, S.J.Xu, W.Wang, P.Li, B.Beaumont, P.Gibart: Applied Physics Letters, 1999, 74[19], 2821-3