Characterization of the origin of band states in the SiC/SiO2 interface

Abstract

Summary form only given. Silicon carbide is a wide bandgap semiconductor whose intrinsic properties make it suited for high-power, high-temperature, and high frequency applications. Additionally, SiC has potential for the fabrication of metal-oxide-semiconductor (MOS) power supplies because it forms a native oxide in the same manner as silicon. The structure of the interface between the native oxide (SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and SiC is not fully understood, yet it is suspected that this interface limits the utilization of MOS power supply applications due to an electron mobility loss. We use scanning transmission electron microscopy (STEM), electron energy loss spectroscopy (EELS), and ab initio calculations to characterize atomic structure and chemistry of the interface. High resolution STEM images with atomic resolution show that the atomically flat interface can be perfectly crystalline or show a disturbed crystalline transition layer at the SiC side depending on process parameters. EELS investigations of the interface indicate that the both sides of the interface are rich in carbon. This interface effect is studied using various annealing conditions in an effect to further quantify outcome. Our results indicate that a high oxidation rate is effectively driving carbon into the SiC and can cause an almost amorphous transition layer. The cumulative effect of the oxidation is an atomically sharp interface with carbon defects leading to electronic states within the bandgap.