Configuration Dependence of Band Gap Narrowing and Localization in Dilute GaAs_{1-x} Bi_x Alloys

TL;DR

This paper investigates how bismuth incorporation affects the band gap and localization in GaAsBi alloys, revealing that at high concentrations, Bi-Bi interactions and strain dominate band gap modifications, which is crucial for optoelectronic applications.

Contribution

It provides a first-principles analysis of band gap narrowing and localization in GaAsBi alloys, highlighting the roles of Bi-Bi interactions and strain at high Bi concentrations.

Findings

Band gap narrowing is dominated by Bi-Bi interactions at high concentrations.

Strain induced by Bi atoms significantly affects electronic properties.

Empirical models are insufficient at high Bi concentrations.

Abstract

Anion substitution with bismuth (Bi) in III-V semiconductors is an effective method for experimental engineering of the band gap Eg at low Bi concentrations, in particular in gallium arsenide (GaAs). The inverse Bi-concentration dependence of Eg has been found to be linear at low concentrations x and dominated by a valence band-defect level anticrossing between As and Bi occupied p levels. This dependence breaks down at high concentrations where empirical models accounting only for the As-Bi interaction are not applicable. Predictive models for the valence band hybridization require a first-principle understanding which can be obtained by density functional theory with the main challenges being the proper description of Eg and the spin-orbit coupling. By using an efficient method to include these effects, it is shown here that at high concentrations Eg is modified mainly by a Bi-Bi p orbital interaction and by the large Bi atom-induced strain. This points to the role of different atomic configurations obtained by varying the experimental growth conditions in engineering arsenide band gaps, in particular for telecommunication laser technology.