Influences of growth conditions on surface properties of MBE grown InN films

We present a study of the InN surface properties investigated in a UHV system (base pressure < x 10-10 mbar) consisting of a surface analytics chamber directly connected to a molecular beam epitaxy (MBE) chamber. Thin InN films were grown on GaN/Al2O3(0001) as well as on GaN/SiC(0001) templates by plasma assisted MBE. The growth was monitored using reflection high energy electron diffraction (RHEED). The dependence of the surface properties (e.g. morphology, stoichiometry and surface electronic structure) on growth conditions was studied using atomic force microscopy as well as X-ray and ultraviolet photoelectron spectroscopy. For stoichiometric and nitrogen rich conditions, the InN grows in the Stranski-Krastanov mode and 3D transmission spots are observed in the RHEED pattern, while a streaky RHEED pattern induced by residual indium on the surface is found for In rich conditions. Depending on In-flux and template 2 x 2, 2 x 1, √(3) x √(3) surface reconstructions were observed. Differences in the core level as well as valence band spectra will be presented and discussed. For nitrogen rich conditions, insertion of excess nitrogen takes place, whereas a shift of all occupied states by 0.3 eV towards EF was observed after indium rich growth