Controlling Polarity of MoTe₂ Transistors for Monolithic Complementary Logic <i>via</i> Schottky Contact Engineering.

Abstract

Two-dimensional (2D) layered molybdenum ditelluride (MoTe₂) crystals, featuring a low energy barrier in the crystalline phase transition and a sizable band gap close to that of silicon, are rapidly emerging with substantial potential and promise for future nanoelectronics. It has been challenging, however, to realize n-type MoTe₂ field-effect transistors (FETs), thus complementary logic, because MoTe₂ FETs mainly exhibit p-type behavior. Here, we report a dopant-free method for controlling polarity of MoTe₂ FETs by modifying Schottky barriers at their MoTe₂-metal contacts <i>via</i> thermal annealing. Upon annealing, MoTe₂ FETs encapsulated by hexagonal boron nitride (h-BN) are consistently changed from hole to electron conduction, displaying an on/off current ratio of 10⁵ or higher. When the MoTe₂ channel is sandwiched between top and bottom h-BN thin layers (h-BN/MoTe₂/h-BN FETs), higher field-effect mobility is attained, up to 48.1 cm² V^-1 s^-1 (hole) and 52.4 cm² V^-1 s^-1 (electron) before and after thermal annealing, respectively. The thermally controlled FET polarity change further enables high-performance MoTe₂ monolithic complementary inverters with gain as high as 36, suggesting this simple and effectual approach may lead to compelling possibilities of rationally controlling transport polarity, on demand, in atomically thin transistors with metal contacts and their 2D integrated circuits.