Effects of growth temperature on Mg-doped GaN epitaxial films grown by plasma-assisted molecular beam epitaxy

A series of Mg-doped GaN films were grown by plasma-assisted molecular beam epitaxy at different temperatures and the resulting surface morphology, cr ystallinity, and electrical propel ties were examined. Although the films w ere grown under N-rich conditions which usually do not give rise to high qu ality films, very smooth surfaces were obtained at high temperatures (T(s)g reater than or equal to 650 degrees C) when doped with Mg. From the informa tion on grain size measured with an atomic force microscope, the activation energy for Ga diffusion was determined to be similar to 1.0 eV. This low v alue is considered to be responsible for promoting the diffusion of Ga atom s on the growing surface and facilitating two-dimensional growth at high te mperatures. It was found, with no surprise, that the concentration of Mg in corporated into the film depends on the growth temperature and that the typ e of electrical conduction in the films is determined by the competition be tween the background electron concentration and Mg-doping. Mg-doped GaN fil ms grown at temperatures between 650 degrees C and 700 degrees C exhibited the p-type electrical properties with smooth surfaces (root-mean-square rou ghness similar to 2 nm) and good crystallinity (full width at half maximum less than or equal to 20 arcmin). (C) 2000 American Vacuum Society. [S0734- 2101(00)00802-2].