Surface structure of hexagonal SiC surfaces: key to crystal growth and interface formation?

Abstract

The atomic structure of the SiC(0001) surface was analysed using low-energy electron diffraction (LEED), scanning tunneling microscopy (STM) and Auger electron spectroscopy (AES). Dependent on the preparation procedure, the surface assumes different complex reconstruction phases. Using an ex situ hydrogen etching procedure, the sample surfaces can be passivated and are covered by a silicon oxide monolayer on top of the SiC bulk. In this state, the surface could serve as a seed to grow epitaxial oxide films for MOS device applications. Subsequent preparation in ultra high vacuum (UHV) by annealing under simultaneous silicon deposition results in a complex (3×3) reconstruction which proves to be almost free of dangling bonds. This surface structure favours the homoepitaxial single polytype growth by enabling incoming particles to diffuse to steps, thus, allowing for an efficient step flow growth mechanism. By further annealing, this phase can be transformed into a ( 3 × 3 )R30° phase, which is characterized by a Si adatom geometry. Variation of the preparation procedure for this structure allows the controlled switch of the surface stacking sequence from hexagonal to cubic stacking, which might be useful as a starting point to grow heterostructures of different SiC polytypes.