EXCITON DYNAMICS IN HOMOEPITAXIAL GAN

Photoluminescence transients have been studied with picosecond resolut ion in homoepitaxial GaN layers grown with MOCVD. In the studied sampl es, with doping concentration in the 10(17) cm(-3) range, the free exc iton (FE) decay time is short, less than 100 ps, mainly due to capture to the shallow impurities, but also: to some extent due to nonradiati ve transitions at defects. The donor bound exciton (DBE) decay time is also short, < 140 ps, indicating some excitation transfer to nonradia tive defects. The acceptor bound exciton (ABE) has a well-defined deca y time of 800 ps below 15 K. The lower decay times for the FE and DBE in the homoepitaxial layers, compared to previously studied heteroepit axial samples, is tentatively ascribed to the much lower dislocation d ensity in the homoepitaxial layers, which suppresses the gettering of nonradiative point defects. (C) 1997 Elsevier Science Ltd.