Metal Semiconductor Field-Effect Transistor with MoS₂/Conducting NiO_x van der Waals Schottky Interface for Intrinsic High Mobility and Photoswitching Speed

Molybdenum disulfide (MoS₂) nanosheet, one of two-dimensional (2D) semiconductors, has recently been regarded as a promising material to break through the limit of present semiconductors. With an apparent energy band gap, it certainly provides a high carrier mobility, superior subthreshold swing, and ON/OFF ratio in field-effect transistors (FETs). However, its potential in carrier mobility has still been depreciated since the field-effect mobilities have only been measured from metal-insulator-semiconductor (MIS) FETs, where the transport behavior of conducting carriers located at the insulator/MoS₂ interface is unavoidably interfered by the interface traps and gate voltage. Moreover, thin MoS₂ MISFETs have always shown large hysteresis with unpredictable negative threshold voltages. Here, we for the first time report MoS₂-based metal semiconductor field-effect transistors (MESFETs) using NiO_x Schottky electrode which makes van der Waals interface with MoS₂. We thus expect that the maximum mobilities or carrier transport behavior of the Schottky devices may hardly be interfered by interface traps or an on-state gate field. Our MESFETs with a few and ∼10 layer MoS₂ demonstrate intrinsic-like high mobilities of 500-1200 cm²/(V s) at a certain low threshold voltage between -1 and -2 V without much hysteresis. Moreover, they work as a high speed and highly sensitive phototransistor with 2 ms switching and ∼5000 A/W, respectively, supporting their high intrinsic mobility results. (Graph Presented).