Strain-tunable energy band parameters of graphene-like GaN

TL;DR

This study uses ab initio calculations to show how in-plane biaxial strain can tune the electronic properties of graphene-like GaN monolayers, including band gap and effective masses, with potential applications in strain sensors and NEMS.

Contribution

It provides the first detailed analysis of strain effects on the structural and electronic properties of hypothetical ML-GaN, revealing tunable band gaps and phase transitions.

Findings

Buckling occurs beyond 7.281% compressive strain.

Band gap reduces to zero at 12.72% tensile strain.

Strain induces a transition from indirect to direct band gap.

Abstract

We present ab initio calculations on the effect of in-plane equi-biaxial strain on the structural and electronic properties of hypothetical graphene-like GaN monolayer (ML-GaN). It was found that ML-GaN got buckled for compressive strain in excess of 7.281 %; buckling parameter increased quadratic-ally with compressive strain. The 2D bulk modulus of ML-GaN was found to be smaller than that of graphene and graphene-like ML-BN, which reflects weaker bond in ML-GaN. More importantly, the band gap and effective masses of charge carriers in ML-GaN were found to be tunable by application of in-plane equi-biaxial strain. In particular, when compressive biaxial strain of about 3 % was reached, a transition from indirect to direct band gap-phase occurred with significant change in the value and nature of effective masses of charge carriers; buckling and tensile strain reduced the band gap - the band gap reduced to 50 % of its unstrained value at 6.36 % tensile strain and to 0 eV at an extrapolated tensile strain of 12.72 %, which is well within its predicted ultimate tensile strain limit of 16 %. These predictions of strain-engineered electronic properties of highly strain sensitive ML-GaN may be exploited in future for potential applications in strain sensors and other nano-devices such as the nano-electromechanical systems (NEMS).