Influence of defects on elastic gate tunneling currents through ultrathin SiO2 gate oxides: predictions from microscopic models

We study theoretically the influence of neutral oxygen vacancies on the mag nitude of elastic tunneling currents through the ultrathin (1.3 nm) gate ox ide of a prototypical metaloxide field-effect transistor with a channel len gth of 50 nm. For the calculation of the gate currents, we have used transm ission coefficients obtained from three-dimensional semiempirical tight-bin ding calculations for a model Si-SiO2-Si junction, and electron distributio n functions based on full-band Monte-Carlo transport simulations. The posit ions of the atoms in the junction were determined by first-principles densi ty-functional calculations. It is found that the gate currents increase sig nificantly (by typically one to three orders of magnitude) in the presence of vacancies having a density around 10(12) cm(-2), provided that the reson ant energy levels lie less than 1 eV above the Si conduction band edge. (C) 2000 Academic Press.