Foundations of ab initio simulations of electric charges and fields at semiconductor surfaces within slab models

TL;DR

This paper develops a slab model framework for simulating electric charges and fields at semiconductor surfaces, emphasizing the control of potential profiles and their impact on surface properties in DFT simulations.

Contribution

It introduces a termination charge slab model with parameters for controlling potential profiles, enabling more accurate simulations of charged semiconductor surfaces.

Findings

Potential profiles depend on surface charge states and can be linear or curved.

Surface electric fields significantly influence surface properties.

The model is demonstrated on GaN and SiC surfaces with DFT simulations.

Abstract

Semiconductor surfaces were divided into charge categories, i.e. surface acceptor, donor and neutral ones that are suitable for simulations of their properties within a slab model. The potential profiles, close to the charged surface states, accounting for explicit dependence of the point defects energy, were obtained. A termination charge slab model was formulated and analyzed proving that two control parameters of slab simulations exist: the slope and curvature of electric potential profiles which can be translated into a surface and volumetric charge density. The procedures of slab model parameter control are described and presented using examples of the DFT simulations of GaN and SiC surfaces showing the potential profiles, linear or curved, depending on the band charge within the slab. It was also demonstrated that the field at the surface may affect some surface properties in a considerable degree proving that verification of this dependence is obligatory for a precise simulation of the properties of semiconductor surfaces.