Direct Observation of Band Gap Renormalization in Layered Indium Selenide

Manipulation of intrinsic electronic structures by electron or hole doping in a controlled manner in Van der Waals layered materials is the key to control their electrical and optical properties. Two dimensional (2D) indium selenide (InSe) semiconductor has attracted attention due to its direct band gap and ultrahigh mobility, as a promising material for optoelectronic devices. In this work, we manipulate the electronic structure of InSe by in situ surface electron doping, and obtain a significant band gap renormalization of ~120 meV directly observed by high-resolution angle resolved photoemission spectroscopy (ARPES). This moderate doping level (carrier concentration of 8.1 × 1012 cm-2) can be achieved by electrical gating in field effect transistors (FETs), demonstrating the potential to design of broad spectral response devices.