Modeling of tunneling current in ultrathin MOS structure with interface trap charge and fixed oxide charge

A model based on analysis of the self-consistent Poisson—Schrodinger equation is proposed to investigate the tunneling current of electrons in the inversion layer of a p-type metal-oxide-semiconductor (MOS) structure. In this model, the influences of interface trap charge (ITC) at the Si—SiO₂ interface and fixed oxide charge (FOC) in the oxide region are taken into account, and one-band effective mass approximation is used. The tunneling probability is obtained by employing the transfer matrix method. Further, the effects of in-plane momentum on the quantization in the electron motion perpendicular to the Si—SiO₂ interface of a MOS device are investigated. Theoretical simulation results indicate that both ITC and FOC have great influence on the tunneling current through a MOS structure when their densities are larger than 10¹² cm⁻², which results from the great change of bound electrons near the Si—SiO₂ interface and the oxide region. Therefore, for real ultrathin MOS structures with ITC and FOC, this model can give a more accurate description for the tunneling current in the inversion layer.