Controlling Polarity of MoTe<sub>2</sub> 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 via 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.