Electronic structure and band alignment at the HfO2∕4H-SiC interface

Abstract

To evaluate the potential of HfO2 as a gate dielectric in SiC power metal-oxide-semiconductor field effect transistors (MOSFETs), the band alignment at the HfO2∕4H-SiC interface was determined by x-ray photoelectron spectroscopy (XPS) measurements and first-principles calculations using density functional theory (DFT). For XPS studies, HfO2 films were grown on 4H-SiC (0001) by a thermal atomic layer deposition process. A valence band offset of 1.74eV and a conduction band offset of 0.70eV were determined based on the valence band and core-level spectra. DFT simulations of the Si-terminated 4H-SiC (0001) surface found a 1×1 relaxed structure whereas simulations of the C-terminated surface observed a 2×1 reconstruction to form C–C dimers. We studied two m-HfO2∕4H-SiC (0001) supercells based on these surfaces and valence band offset values of 2.09 and 1.47eV, and conduction band offset values of 0.35 and 0.97eV, respectively, were predicted. The consistently low conduction band offset may not provide an adequate barrier height for electron injection from the substrate and further electrical studies are necessary to determine the viability of integrating HfO2 in SiC power MOSFETs.