Spatially modified layer properties related to the formation of gallium droplets on GaN(0001) surfaces during plasma-assisted molecular-beam epitaxy

The surface morphology and the spatial distribution of defect-related lumin escence of GaN(0001) layers grown by plasma-assisted molecular-beam epitaxy under gallium-rich conditions has been investigated. Droplets of liquid ga llium form on the surface during growth and lead to distinct spiral hillock s under the droplet. The droplets are surrounded by extended voids which po int to an incomplete gallium adlayer on the GaN surface during growth at th e droplet boundary. Cathodoluminescence spectra indicate an enhanced intens ity in the yellow spectral range for the GaN under the droplets which is at tributed to a change in the local density of point defects in the layer. (C ) 2001 American Institute of Physics.