The optical properties of few-layer InSe

Few-layer InSe draws tremendous research interests owing to the superior electronic and optical properties. It exhibits a high carrier mobility up to more than 1000 cm2/Vs at room temperature. The strongly layer-tunable bandgap spans a large spectral range from near-infrared to the visible. In this perspective, we systematically review the optical properties of few-layer InSe. First, the intrinsic optical and electronic properties are introduced. Compared to other two-dimensional materials, the light-matter interaction of few-layer InSe is unusual. The bandgap transition is inactive or extremely weak for in-plane polarized light, and the emission light is mainly polarized along the out-of-plane direction. Second, we will present several schemes to tune the optical properties of few-layer InSe such as external strain, surface chemical doping, and van der Waals interfacing. Third, we survey the applications of few-layer InSe in photodetection and heterostructures. Overall, few-layer InSe exhibits great potentials not only in fundamental research but also in electronic and optoelectronic applications.