Enhancement of Electronic and Optoelectronic Performance of the InSe Multilayer by Surface Transfer Engineering

Indium selenide (InSe) is considered an ideal two-dimensional material for infrared light detection owing to its high carrier mobility and narrow band gap. Here, we demonstrate a considerable enhancement in the performance of an InSe phototransistor via surface functionalization with an In layer. Electron mobility in InSe increased by almost 59 times after surface functionalization using a 20 nm thick In layer. Furthermore, compared with InSe/h-BN, In/InSe/h-BN-based photodetectors exhibited an almost 3-fold increase in photoresponsivity and external quantum efficiency at 940 nm owing to an enhancement of the surface charge transfer. First-principles calculation and Raman and photoluminescence spectroscopy analyses confirmed the occurrence of a considerable surface charge transfer at the In/InSe interface. The tunability of the surface transfer efficiency via doping establishes the potential of InSe for future use in optoelectronic devices based on two-dimensional materials.