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Growth of SiC wafer material, of heterostructures with alternating SiC crystal modifications (polytypes), and of oxide layers on SiC are of importance for potential electronic device applications. By investigation of hexagonal SiC surfaces the importance of atomic surface structure for control of the respective growth processes involved is elucidated. Different reconstruction phases prepared by ex situ hydrogen treatment or by Si deposition and annealing in vacuum were analyzed using scanning tunneling microscopy (STM), Auger electron spectroscopy (AES) and low-energy electron diffraction (LEED) crystallography. The extremely efficient dangling bond saturation of the SIC(0001)-(3 × 3) phase allows step flow growth for monocrystalline homoepitaxial layers. A switch to cubic layer stacking can be induced on hexagonal SIC(0001) samples when a (&radic3; × &radic3;)R30° phase is prepared. This might serve as seed for polytype heterostructures. Finally, we succeeded in preparing an epitaxially well matching silicon oxide monolayer with (&radic3; ° &radic3;)R30° periodicity on both SIC(0001) and SiC(000&1macr;). This initial layer promises to facilitate low defect density oxide films for MOS devices. [ABSTRACT FROM AUTHOR]

The atomic structure of silicon carbide (SiC) surfaces in hexagonal orientation is investigated with the main emphasis put on surface morphology and dangling-bond saturation either by adspecies or by surface reconstruction. By using quantitative low-energy electron diffraction (LEED) intensity analysis, the atomic geometry immediately after ex situ chemical treatment is determined for 4H and 6H samples in both hexagonal orientations and a 3C-SiC(111) surface. The step structure is found to be directly related to the polytype of the samples from morphology studies by using scanning-tunneling microscopy (STM). This is in agreement with the surface layer stacking sequence determined in the LEED analysis. Dangling bonds of the topmost surface atoms are fully saturated by adspecies that remain from the chemical preparation. Reconstruction phases prepared under ultra-high vacuum conditions are investigated using the in situ combination of LEED and STM. Here the number of dangling bonds is reduced by a reconstruction pattern that involves adatoms or adclusters for the more silicon rich-phases and by a commensurate overlayer of large periodicity in the more carbon-rich structures. [ABSTRACT FROM AUTHOR]