ZnSe/GaAs(001) heterostructures with defected interfaces: structural, thermodynamic and electronic properties

TL;DR

This study uses ab-initio calculations to analyze the structural, thermodynamic, and electronic properties of defected ZnSe/GaAs(001) heterostructures, revealing conditions favoring defected configurations and their impact on band offsets.

Contribution

It provides new insights into the stability and electronic properties of defected interfaces in ZnSe/GaAs heterostructures, supporting experimental findings of defected compounds.

Findings

Defected configurations can be thermodynamically favored under certain conditions.

Calculated band offsets align with experimental measurements.

Presence of vacancies and atomic rearrangements affects interface charge neutrality.

Abstract

We have performed accurate \emph{ab--initio} pseudopotential calculations for the structural and electronic properties of ZnSe/GaAs(001) heterostructures with interface configurations accounting for charge neutrality prescriptions. Beside the simplest configurations with atomic interdiffusion we consider also some configurations characterized by As depletion and cation vacancies, motivated by the recent successfull growth of ZnSe/GaAs pseudomorphic structures with minimum stacking fault density characterized by the presence of a defected (Zn,Ga)Se alloy in the interface region. We find that--under particular thermodynamic conditions--some defected configurations are favoured with respect to undefected ones with simple anion or cation mixing, and that the calculated band offsets for some defected structures are compatible with those measured. Although it is not possible to extract indications about the precise interface composition and vacancy concentration, our results support the experimental indication of (Zn,Ga)Se defected compounds in high-quality ZnSe/GaAs(001) heterojunctions with low native stacking fault density. The range of measured band offset suggests that different atoms at interfaces rearrange, with possible presence of vacancies, in such a way that not only local charges but also ionic dipoles are vanishing.