Electronic properties of SiC and AlN surfaces and interfaces

Surface properties are important in semiconductor processing as the surface preparation can affect electronic properties. For this reason, the surfaces of SiC and AlN have been studied to determine how the electronic properties vary with surface treatment. The surface electronic structure of clean 6H silicon carbide (SiC) has been investigated by Angle Resolved Ultraviolet Photoelectron Spectroscopy (ARUPS). The surfaces were prepared by in situ silane exposure, and clean well ordered surfaces were obtained. The surface structures were characterized with LEED, Auger electron spectroscopy, and XPS. The results demonstrated the removal of oxygen and other contamination. By variation of the silane exposure and temperature, surfaces were examined that exhibited {dollar}3times 3,{dollar} {dollar}1times 1{dollar} and {dollar}sqrt{lcub}3{rcub}times sqrt{lcub}3{rcub}{dollar} surface diffraction. Features were observed in the ARUPS spectra that were attributed to the presence of surface states/surface resonances. The surface dispersion of the states are reported. Hydrogen exposure resulted in the removal of the surface state.; The characteristics of epitaxial AlN grown on SiC has also been studied. We determine that the surface exhibits a negative electron affinity (NEA). Samples studied were grown by ECR plasma, or gas source molecular beam epitaxy (GSMBE).; This study also presents results of UV-photoemission measurements of the surface and interface properties of heteroepitaxial AlGaN on 6H-SiC. We expect that as AlN/SiC exhibits an NEA surface, that there is a transition point in the AlGaN solid solution. In this study AlGaN alloy films were grown by organometallic vapor phase epitaxy (OMVPE), or by in situ GSMBE. All analysis took place in an integrated UHV system which included the analysis techniques, and a surface processing chamber. The OMVPE alloy samples were transported in air to the surface characterization system. The surface electronic states were characterized by UV photoemission to determine whether the electron affinity was positive or negative. The AlN samples exhibited the characteristics of a NEA while the GaN and low Al AlGaN samples did not. It was determined that the affinity transition point was 65% Al content.