Strain-tunable energy band parameters of graphene-like GaN

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).