Growth of aluminum oxide on silicon carbide with an atomically sharp interface

The development of SiC wafers with properties suitable for electronic device fabrication is now well established commercially. A critical issue for developing metal-oxide-semiconductor field effect transistor devices of SiC is the choice of dielectric materials for surface passivation and insulating coatings. Although SiO₂ grown thermally on SiC is a possibility for the gate dielectric, this system has a number of problems related to the higher band gap of SiC, which energetically favors more interface states than for SiO₂ on Si, and the low dielectric constant of SiO₂ leading to 2.5× higher electric fields across the oxide than in the surface of SiC, and to a premature breakdown at the higher fields and higher temperatures that SiC devices are designed to operate under. As a replacement for SiO₂, amorphous Al₂O₃ thin film coatings have some strong advocates, both for n- and p-type SiC, due to the value of its band gap and the position of its band edges with respect to the band edges of the underlying semiconductor, a number of other material properties, and not the least due to the advances of the atomic-layer-deposition process. Exploring the fact that the chemical bonding of Al₂O₃ is the strongest among the oxides and therefore stronger than in SiO₂, the authors have previously shown how to form an Al₂O₃ film on Si (111) and Si (100), by simply depositing a few atomic layers of Al on top of an ultrathin (0.8 nm) SiO₂ film previously grown on Si surfaces [Si (111) and Si (100)] and heating this system up to around 600 °C (all in ultrahigh vacuum). This converts all the SiO₂ into a uniform layer of Al₂O₃ with an atomically sharp interface between the Al₂O₃ and the Si surface. In the present work, the same procedures are applied to form Al₂O₃ on a SiC film grown on top of Si (111). The results indicate that a similar process, resulting in a uniform layer of 1-2 nm of Al₂O₃ with an atomically sharp Al₂O₃/SiC interface, also works in this case.