Band alignment of metal/amorphous-oxide interface using atomic orbitals projection of plane-wave: a first principle study at the Al/a-SiO2 interface

TL;DR

This study introduces a novel LCAO projection method for accurately determining band alignment at metal/amorphous-oxide interfaces, overcoming limitations of classical approaches due to amorphous disorder.

Contribution

The paper presents a new wave-function projection technique based on LCAO that captures interface effects for precise band alignment in amorphous oxide interfaces.

Findings

Good agreement with experimental data for Al/a-SiO2 interface

Identification of a space charge region causing non-linear band bending

Observation of virtual oxide thinning reducing dielectric strength

Abstract

Amorphous insulating oxides play a significant role in the contemporary electronic industry. Understanding the band alignment of heterogeneous interfaces containing amorphous structures helps to better control the carrier transport property at the interface. Classical band offset methods developed previously line-up eigenlevels with respect to an ideal bulk reference or vacuum level. However, the local disorder of amorphous structures makes the bulk reference ambiguous. Therefore, classical methods cannot be applied. In this study, we introduce a new approach based on the Linear Combination of Atomic Orbital (LCAO) projection of wave-function to line-up bands at metal/oxide interfaces. The LCAO projection of wave-function accounts for all metal/oxide interface effects, such as build-in voltage, interface dipole, virtual oxide thinning, barrier deformation, etc. Therefore, it provides accurate band alignments. Calculations performed at an Al/amorphous-SiO2 exhibit a good agreement between existing experiments and simulation data. We Also observed a space charge region at the interface resulting in non-linear band bending in the oxide, which virtually decreases its thickness, hence lowering the dielectric strength.