Investigation of Thickness-Dependent Optical and Optoelectronic Properties of Mechanically Exfoliated GaSe Nanoflakes

Two-dimensional (2D)-layered materials are in prime focus of the researchers because of their excellent optoelectronic properties at the micro- and nanolevels. In this work, we have conducted a comprehensive study on the thickness-dependent optical and optoelectronic properties of the mechanically exfoliated GaSe thin films. Raman and photoluminescence measurements were done on the ultrathin GaSe flakes of different thicknesses to study the change in their phonon modes and optical properties. To understand the optoelectronic properties, metal–semiconductor–metal (MSM) photodetectors were fabricated on GaSe flakes. The performance of the photodetectors was measured in terms of the figure-of-merit parameters of a photodetector such as photoresponsivity ( R λ ) and external quantum efficiency (EQE). Thicker GaSe flakes provided better performance, with a maximum value of R λ and EQE of ∼0.21 A/W and ∼42, respectively, at 620 nm, as compared to thinner flakes. We believe our study could help to boost the development of future high-performance optoelectronic devices based on quasi-2D materials.