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 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 similar to 120 meV directly observed by high-resolution angle resolved photoemission spectroscopy. This moderate doping level (carrier concentration of 8.1 x 10(12) cm(-2)) can be achieved by electrical gating in field effect transistors, demonstrating the potential to design of broad spectral response devices.