Enhancement of photoluminescence and hole mobility in 1-to 5-layer InSe due to the top valence-band inversion: strain effect

摘要

Recently, two-dimensional (2D) few-layer InSe nanosheets have become one of the most interesting materials due to their excellent electron transport, wide bandgap tunability and good metal contact. However, their low photoluminescence (PL) efficiency and hole mobility seriously restrict their application in 2D InSe-based nano-devices. Here, by exerting a suitable compressive strain, a remarkable modification for the electronic structure and the optical and transport properties of 1- to 5-layer InSe has been confirmed by powerful GW-BSE calculations. Both top valence band inversion and indirect-to-direct bandgap transition are induced; the light polarization is reversed from Ec to E perpendicular to c; and the PL intensity and hole mobility are enhanced greatly. Surprisingly, under 6 compressive strain, the light emission of monolayer InSe with E perpendicular to c is allowed at 2.58 eV, which has never been observed previously. Meanwhile, for the 2D few-layer InSe, the PL with E perpendicular to c polarization increases over 10 times in intensity and has a blue-shift at about 0.6-0.7 eV, and the hole mobility increases two orders of magnitude up to 10(3) cm(2) V-1 s(-1), as high as electron mobility. The strained few-layer InSe are thus a promising candidate for future 2D electronic and optoelectronic nano-devices.