High electron mobility and transverse negative magnetoresistance in van der Waals material Nb2GeTe4

Abstract

Two-dimensional (2D) semiconductors with high charge-carrier mobility and exotic quantum properties are of great importance for the design of outstanding electronic devices. Here we report the single crystal growth of van der Waals material Nb₂GeTe₄, which exhibits very high mobility and unusual transverse negative magnetoresistance (MR) from our transport-property-measurements. Nb₂GeTe₄ adopts a Te–Nb(Ge)–Te sandwiched layer structure and exhibits a narrow-gap semiconducting behavior. Based on ultraviolet–visible–near infrared (UV-vis-NIR) optical measurement, the optical band gap of Nb₂GeTe₄ is determined to be around 0.39 eV. The high electron mobility of the Nb₂GeTe₄ bulk crystal at room temperature, 424.37 cm² V⁻¹ s⁻¹, is comparable to those of the current state-of-the-art high-mobility layered materials, making Nb₂GeTe₄ competitive for the design of 2D electronic devices. An anomalous negative magnetoresistance is also observed in Nb₂GeTe₄ below 10 K with different field dependency, where the maximum MR reaches ∼−31% at 5 K and 5 T.