Nb₂SiTe₄: A Stable Narrow-Gap Two-Dimensional Material with Ambipolar Transport and Mid-Infrared Response

Two-dimensional (2D) materials with narrow band gaps (∼0.3 eV) are of great importance for realizing ambipolar transistors and mid-infrared (MIR) detections. However, most of the 2D materials studied to date have band gaps that are too large. A few of the materials with suitable band gaps are not stable under ambient conditions. In this study, the layered Nb₂SiTe₄ is shown to be a stable 2D material with a band gap of 0.39 eV. Field-effect transistors based on few-layer Nb₂SiTe₄ show ambipolar transport with a similar magnitude of electron and hole current and a high charge-carrier mobility of ∼100 cm² V^-1 s^-1 at room temperature. Optoelectronic measurements of the devices show clear response to an MIR wavelength of 3.1 μm with a high responsivity of ∼0.66 AW^-1. These results establish Nb₂SiTe₄ as a good candidate for ambipolar devices and MIR detection.