Gate leakage current in double-gate MOSFETs with Si/SiO<inf>2</inf> interface model from first principle calculations

Abstract

The band gap and electric permeability changes across the Si/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface of a MOS device were calculated based on the density function theory. The band gap changes non-abruptly at the interface with a transition region of 5 A toward the oxide. The calculated dielectric constants change almost abruptly at Si/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface. Thus-obtained band gap profile and spatial behavior of dielectric constants were used in a device simulation of an ultra-thin-body n-type double-gate MOSFET. The potential profile in the channel was calculated by self-consistently solving the two-dimensional Poisson-Schrodinger equations. The gate leakage current was calculated accurately using the three-terminal non-equilibrium Green's function approach. The effect of the band gap transition across the Si/SiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> interface on the device performance is investigated in detail.