Large‐Area Tellurium/Germanium Heterojunction Grown by Molecular Beam Epitaxy for High‐Performance Self‐Powered Photodetector

Abstract As an attractive elemental semiconductor material, p‐type tellurium (Te) with a narrow bandgap provides high carrier mobility, strong light–matter interactions in a wide spectral range, and good chemical stability, which enlightens the potential in optoelectronic devices. However, the applications are impeded by weak carrier separation and vague potential in scaling‐up. In this work, the integration of Te and conventional semiconductor germanium (Ge) is designed. Through molecular beam epitaxy (MBE) method, large‐area and uniform Te films with high crystallinity are directly deposited on the Ge substrates. The difference in work function between Te and Ge layer leads to a built‐in electric field, which can effectively enhance the carrier separation. As a result, a self‐powered splendid photovoltaic performance is observed in the MBE grown Te/Ge vertical heterojunction with current on/off ratio over 10 3 , responsivity ( R ) 523 mA W −1 , and specific detectivity ( D *) 9.50 × 10 10 cm Hz 1/2 W −1 when illuminated by near‐infrared light (980 nm, 2.15 µW cm −2 ). Furthermore, excellent stability and high response speed of the ultrathin heterostructure offer a significant application value for multipurpose photoelectric devices.