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

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.