Band Alignment and High-Performance Unbiased Vis–NIR Photodetection of Semimetal Bi ₄ Se ₃ /Si Heterostructures

Semimetals have recently attracted much research interest in electronics as contact layers due to their appealing physical properties, such as a layered structure and a low density of states at the Fermi level. Herein, we study the band alignment and unbiased visible-to-near-infrared (Vis-NIR) photodetection of semimetal Bi₄Se₃/Si heterostructures. High-quality Bi₄Se₃/Si heterostructures are prepared by epitaxially growing (001)-orientated Bi₄Se₃ films on H-passivated Si(111) substrates. Ohmic and Schottky contact properties of Bi₄Se₃ to <i>n</i>- and <i>p</i>-Si are revealed. Analysis of the temperature dependence of reverse thermionic emission suggests that the height of the Schottky barrier at the Bi₄Se₃/<i>p</i>-Si junction is 0.37 eV, thus depicting its band alignment. A photodiode consisting of the Bi₄Se₃/<i>p</i>-Si heterostructure exhibits fast unbiased broadband detection in Vis-NIR regions (405-1064 nm) with ultralow dark current (0.5 nA), good responsivity (288 mA W^-1) and decent detectivity (3.28 × 10⁸ Jones) at 980 nm, and excellent stability.