INFLUENCE OF MAGNESIUM DOPING ON THE STRUCTURAL-PROPERTIES OF GAN LAYERS

We investigate the incorporation of magnesium in gallium nitride (GaN) films deposited on (0001) sapphire (c-Al2O3) substrates by low-pressu re metalorganic chemical vapor-phase deposition (MOCVD). The growth, s tructure and optical properties of GaN samples with a dopant concentra tion ranging from 10(17) to 10(21) cm(-3) have been studied using tran smission electron microscopy and micro-Raman spectroscopy. The growth rate and sample quality are strongly influenced by the amount of magne sium incorporated in the sample, with the inclusion of cubic GaN on th e otherwise hexagonal material and a disruption of the two-dimensional growth for the highest dopant concentrations. The presence of the cub ic phase is accompanied by the formation of large triangular islands d ue to a local increase of growth rate for a dopant concentration excee ding 10(20) cm(-3).