Functional surface reconstructions of hexagonal SiC

The basal surfaces of hexagonal SiC exhibit a large variety of surface reconstructions that develop under a similarly rich variety of sample preparations. A subset of these surface phases, which have been investigated in structural detail using scanning tunnelling microscopy and quantitative low-energy electron diffraction, is described and shown to offer the scope to be used for the formation of SiC-based semiconductor devices. The phases discussed are the (3 x 3) and (root3 x root3)R30degrees reconstructions for the (0001) surfaces of 4H- and 6H-SiC and the oxygen-uptake-driven (root3 x root3)R30degrees-SiOX reconstructions of these polytypes for both the (0001) and the (000 (1) over bar) surface orientations. We show that the (3 x 3) reconstruction corresponds to a highly passivated surface that facilitates hexagonal single-crystal growth, while Suitable preparation of the (root3 x root3)R30degrees reconstruction favours a switch to cubic growth and hence to the formation of a heterojunction. The (root3 x root3)R30degrees-SiOX reconstructions promise to form defect-free interfaces to insulating silicon oxide films, which is important for device applications.