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

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 1.74 eV and a conduction band offset of 0.70 eV were determined based on the valence band and core-level spectra. DFT simulations of the Si-terminated 4H-SiC (0001) surface found a 1x1 relaxed structure whereas simulations of the C-terminated surface observed a 2x1 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 1.47 eV, and conduction band offset values of 0.35 and 0.97 eV, 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. (c) 2007 American Institute of Physics.