Self-Powered Broadband Photodetector Based on a Monolayer InSe p - i - n Homojunction

The two-dimensional homojunction is promising in electronic and optoelectronic applications. However, its performance is restricted by lattice mismatch and the depletion region. Here, we construct a monolayer $\mathrm{In}\mathrm{Se}$-based p-i-n homojunction photodetector. It presents high photoelectric conversion with a wide light response in the photon-energy range from 1.4 to 5 eV, which induces a photocurrent density of 13.13 nA ${\mathrm{m}}^{\ensuremath{-}1}$ and a photoresponsivity of 0.022 A ${\mathrm{W}}^{\ensuremath{-}1}$. Moreover, the gate voltage improves the photocurrent and photoresponsivity almost fourfold. Additionally, the increasing dielectric constant of the substrate decreases the photocurrent spectral width, and a low doping concentration is suitable for photodetectors due to high mobility. These results indicate that the two-dimensional p-i-n homojunction is promising for future photoelectric devices.