Properties of Bare and Thin-Film-Covered GaN(0001) Surfaces

In this paper, the surface properties of bare and film-covered gallium nitride (GaN) in wurtzite form, (0001) oriented, are summarized. Thin films of several elements-manganese, nickel, palladium, arsenic, and antimony-were formed by the physical vapor deposition method. The results of the bare surfaces, as well as the thin film/GaN(0001) phase boundaries presented, were characterized by X-ray and ultraviolet photoelectron spectroscopies (XPS, UPS). Basic information on the electronic properties of GaN(0001) surfaces are shown. Different behaviors of the thin films, after postdeposition annealing in ultrahigh vacuum conditions such as surface alloying and subsurface dissolving and desorbing, were found. The metal films formed surface alloys with gallium (MnGa, NiGa, PdGa), while the semimetal (As, Sb) layers easily evaporate from the GaN(0001) surface. However, the layer in direct contact with the substrate could react with it, modifying the surface properties of GaN(0001).