Effect of Gallium Nitride Film Growth Conditions on Surface Segregation

The micro-and nanomorphology and local composition of gallium nitride (GaN) films produced by four different procedures have been studied with the aim of detecting autosegregation phenomena. As a result, a complex autosegregation picture has been demonstrated and discussed. Independent of the growth procedure, all of the gallium nitride films have nonstoichiometric chemical compositions (gallium deficiency), with a degree of nonstoichiometry ranging from similar to 0.30 to < 0.10. We discuss the segregation mechanism, which presumably involves predominant selective diffusion of nitrogen atoms to the surface.