Inhomogeneities in heterostructures, due to dislocations and limitations in the growth process, were studied. The electron occupancy in acceptor-like states along dislocations in wurtzite-type material were modelled. The reduction in free electron concentration and mobility was calculated as a function of dopant concentration, dislocation concentration and compensation. The mobility and photoluminescence in heterostructures were also studied. Since the molecular beam epitaxial growth took place on insulating substrates in a charged N plasma, effects due to substrate size were expected. The mobility was a factor of 2 larger on 5cm substrates, as compared with ¼- and ⅛-sized pieces. Photoluminescence variations that depended upon substrate size and shape were also observed.

Limitations in MBE-Grown GaN and AlGaN/GaN Due to Dislocations and Lateral Inhomogeneities. K.K.M.N.Gurusinghe, F.Fälth, T.G.Andersson: Journal of Crystal Growth, 2001, 227-228, 381-5