Direct tunneling through high-$\kappa$ amorphous HfO$_2$: effects of chemical modification

TL;DR

This study uses first principles modeling to show that chemical doping of amorphous HfO$_2$ can significantly reduce quantum tunneling leakage in MOS devices, providing insights into microscopic tunneling physics.

Contribution

It demonstrates that doping N and Al atoms in the middle of amorphous HfO$_2$ effectively reduces tunnel leakage, a novel approach for leakage mitigation in high-$"kappa$ dielectrics.

Findings

Doping N and Al reduces tunnel leakage by over an order of magnitude.

Other modifications can increase tunneling or cause band bending, which are undesirable.

Microscopic analysis reveals how impurities affect electron transmission.

Abstract

We report first principles modeling of quantum tunneling through amorphous HfO$_2$ dielectric layer of metal-oxide-semiconductor (MOS) nanostructures in the form of n-Si/HfO$_2$/Al. In particular we predict that chemically modifying the amorphous HfO$_2$ barrier by doping N and Al atoms in the middle region - far from the two interfaces of the MOS structure, can reduce the gate-to-channel tunnel leakage by more than one order of magnitude. Several other types of modification are found to enhance tunneling or induce substantial band bending in the Si, both are not desired from leakage point of view. By analyzing transmission coefficients and projected density of states, the microscopic physics of electron traversing the tunnel barrier with or without impurity atoms in the high-$\kappa$ dielectric is revealed.