Terraces at ohmic contact in SiC electronics: Structure and electronic states

Combining transmission electron microscopy with first-principles calculations, atomic structures of terraces at the contacts in silicon carbide devices are investigated and bridged to their electronic properties at an atomic scale. Experimentally, newly formed carbide Ti ₃SiC ₂ is demonstrated to bond directly to silicon carbide in the terrace region in an epitaxial and atomically ordered fashion, regardless of dimension of terraces. Further first-principles calculations reveal gap states in the semiconductor layers and a substantial charge accumulation around terraces in a connected and broadly distributed manner. The presence of gap states at Fermi energy and the likelihood to serve as electron conduction channels to allow current flow over the semiconductor identify the terraces as one of the origins underlying the ohmic contact in silicon carbide electronics. Such a combined experimental and theoretical investigation provides insight into the complex atomic and electronic structures of buried terraces, which should be applicable to addressing contact issues of interest in other electronic devices.