Epitaxial growth of 2D gallium selenide flakes for strong nonlinear optical response and visible-light photodetection

As an emerging group III-VI semiconductor two-dimensional (2D) material, gallium selenide (GaSe) has attracted much attention due to its excellent optical and electrical properties. In this work, high-quality epitaxial growth of few-layer GaSe nanoflakes with different thickness is achieved via chemical vapor deposition (CVD) method. Due to the non-centrosymmetric structure, the grown GaSe nanoflakes exhibits excellent second harmonic generation (SHG). In addition, the constructed GaSe nanoflake-based photodetector exhibits stable and fast response under visible light excitation, with a rise time of 6 ms and decay time of 10 ms. These achievements clearly demonstrate the possibility of using GaSe nanoflake in the applications of nonlinear optics and (opto)-electronics.