Engineering direct-indirect band gap transition in wurtzite GaAs nanowires through size and uniaxial strain

TL;DR

This study investigates how size and uniaxial strain influence the electronic band gap nature of wurtzite GaAs nanowires, enabling control over their direct or indirect band gap properties for potential optoelectronic applications.

Contribution

It demonstrates that applying uniaxial strain can switch the band gap of thin GaAs nanowires from indirect to direct, providing a method to engineer their electronic properties.

Findings

Nanowire diameter below ~28 Å causes a direct-to-indirect band gap transition.

Uniaxial strain can induce an indirect-to-direct band gap transition in thin nanowires.

Critical strain values depend on the energy crossover of conduction band states.

Abstract

Electronic structures of wurtzite GaAs nanowires in the [0001] direction were studied using first-principles calculations. It was found that the band gap of GaAs nanowires experience a direct-to-indirect transition when the diameter of the nanowires is smaller than ~28 {\AA}. For those thin GaAs nanowires with an indirect band gap, it was found that the gap can be tuned to be direct if a moderate external uniaxial strain is applied. Both tensile and compressive strain can trigger the indirect-to-direct gap transition. The critical strains for the gap-transition are determined by the energy crossover of two states in conduction bands.