A two-dimensional semiconductor transistor with boosted gate control and sensing ability.

Abstract

Transistors with exfoliated two-dimensional (2D) materials on a SiO₂/Si substrate have been applied and have been proven effective in a wide range of applications, such as circuits, memory, photodetectors, gas sensors, optical modulators, valleytronics, and spintronics. However, these devices usually suffer from limited gate control because of the thick SiO₂ gate dielectric and the lack of reliable transfer method. We introduce a new back-gate transistor scheme fabricated on a novel Al₂O₃/ITO (indium tin oxide)/SiO₂/Si "stack" substrate, which was engineered with distinguishable optical identification of exfoliated 2D materials. High-quality exfoliated 2D materials could be easily obtained and recognized on this stack. Two typical 2D materials, MoS₂ and ReS₂, were implemented to demonstrate the enhancement of gate controllability. Both transistors show excellent electrical characteristics, including steep subthreshold swing (62 mV dec^-1 for MoS₂ and 83 mV dec^-1 for ReS₂), high mobility (61.79 cm² V^-1 s^-1 for MoS₂ and 7.32 cm² V^-1 s^-1 for ReS₂), large on/off ratio (~10⁷), and reasonable working gate bias (below 3 V). Moreover, MoS₂ and ReS₂ photodetectors fabricated on the basis of the scheme have impressively leading photoresponsivities of 4000 and 760 A W^-1 in the depletion area, respectively, and both have exceeded 10⁶ A W^-1 in the accumulation area, which is the best ever obtained. This opens up a suite of applications of this novel platform in 2D materials research with increasing needs of enhanced gate control.