Full-band tunneling in high-kappa oxide MOS structures

In this paper, we investigate the tunneling properties of ZrO2 and HfO2 high-kappa oxides, by applying quantum mechanical methods that include the full-band structure of Si and oxide materials. Semiempirical sp(3)s*d tight-binding parameters have been determined to reproduce ab-initio band dispersions. Transmission coefficients and tunneling currents have been calculated for Si/ZrO2/Si and Si/HfO2/Si MOS structures, showing a very low gate leakage current in comparison to SiO2-based structures with the same equivalent oxide thickness. The complex band structures of ZrO2 and HfO2 have been calculated and used to develop an energy-dependent effective tunneling mass model. We show that effective mass calculations based on this model yield tunneling currents in close agreement with full-band results.