Progress of MoS2 Negative-Capacitance Field-Effect Transistor

Power consumption is a bottleneck restricting the development of integrated circuits. The MoS₂ negative-capacitance field-effect transistor (NC-FET), which introduces new ferroelectric materials into the gate, could break the sub-threshold swing switching limit of traditional field-effect transistors, and is expected to work at extremely low power supply voltages, thereby reducing power consumption and maintaining high performance.

At the same time, the atomic layer thickness of molybdenum disulfide (MoS₂) is immune to short channel effects, holds the advantages of high mobility, extremely low off-state current and CMOS compatible manufacturing process, and is an optional channel for advanced transistors.

NC-FET is one of a number of recently developed steep-slope transistor technologies that it is hoped will enable the lower-power electric industry. The concept relies on the use of ferroelectric materials whose S-shape electric-field characteristic leads to an unstable negative-capacitance region. It is believed that the NC-FET state could be stabilized when connected in series with a conventional dielectric material and when used in a transistor gate, it should lead to the lower-voltage switching.

Some recent experiments have shown that MoS₂ negative-capacitance field-effect transistors can achieve sub-threshold swings below 60mV/dec. However, these studies have only achieved devices with longer channels (>500 nm), and have not utilized the advantages of the negative capacitance effect in short-channel transistors.

In response to this problem, the team of Academician Ming Liu reduced the channel length of molybdenum disulfide NC-FET to 83 nanometers for the first time through the design and optimization of device parameters and manufacturing processes and achieved an ultra-low subthreshold swing (SS_min=17.23 mV/dec and SS_ave=39 mV/dec).

Compared with the reference device, the average subthreshold swing is increased from 220 mV/dec to 39 mV/dec, and the channel current is increased by 346 times and 26 times at VGS=0 V and 1.5 V, respectively. This work promotes the continuous shrinking of the MoS₂ negative-capacitance field-effect transistor size, which has a certain significance for such devices for low-power applications.

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