Heterovalent interlayers and interface states: an ab initio study of GaAs/Si/GaAs (110) and (100) heterostructures

TL;DR

This study uses ab initio calculations to analyze localized interface states in GaAs/Si/GaAs heterostructures with different orientations and Si monolayers, revealing how interface states evolve and differ between (110) and (100) orientations.

Contribution

It provides a detailed ab initio analysis of interface states in GaAs/Si/GaAs heterostructures, linking states across different orientations and Si layer thicknesses, and discusses conditions for localized state existence.

Findings

Interface states differ significantly between (110) and (100) orientations.

Localized states are found deeper in the valence band for (110) structures.

The evolution of interface states from binary to ternary junctions is characterized.

Abstract

We have investigated ab initio the existence of localized states and resonances in abrupt GaAs/Si/GaAs (110)- and (100)-oriented heterostructures incorporating 1 or 2 monolayers (MLs) of Si, as well as in the fully developed Si/GaAs (110) heterojunction. In (100)-oriented structures, we find both valence- and conduction-band related near-band edge states localized at the Si/GaAs interface. In the (110) systems, instead, interface states occur deeper in the valence band; the highest valence-related resonances being about 1 eV below the GaAs valence-band maximum. Using their characteristic bonding properties and atomic character, we are able to follow the evolution of the localized states and resonances from the fully developed Si/GaAs binary junction to the ternary GaAs/Si/GaAs (110) systems incorporating 2 or 1 ML of Si. This approach also allows us to show the link between the interface states of the (110) and (100) systems. Finally, the conditions for the existence of localized states at the Si/GaAs (110) interface are discussed based on a Koster-Slater model developed for the interface-state problem.