A subthermionic tunnel field-effect transistor with an atomically thin channel.

A new type of device, the band-to-band tunnel transistor, which has atomically thin molybdenum disulfide as the active channel, operates in a fundamentally different way from a conventional silicon (MOSFET) transistor; it has turn-on characteristics and low-power operation that are better than those of state-of-the-art MOSFETs or any tunnelling transistor reported so far. Traditional transistor technology is fast approaching its fundamental limits, and two-dimensional semiconducting materials such as molybdenum disulfide (MoS2) are seen as possible replacements for silicon in a next generation of high-density, lower-power chip electronics. A particularly promising prospect is their potential in band-to-band tunnel transistors, which operate in a fundamentally different way from conventional silicon (MOSFET) transistors. So far, few such devices with overall characteristics better than silicon transistors have been demonstrated. Now Kaustav Banerjee et al. have built a tunnel transistor by making a vertical structure with atomically thin MoS2 as the active channel and germanium as the source electrode. It has turn-on characteristics and low-power operation that are better than those of existing silicon transistors, and the results will be of interest in a range of electronic applications including low-power integrated circuits, as well as ultra-sensitive bio sensors or gas sensors. The fast growth of information technology has been sustained by continuous scaling down of the silicon-based metal–oxide field-effect transistor. However, such technology faces two major challenges to further scaling. First, the device electrostatics (the ability of the transistor’s gate electrode to control its channel potential) are degraded when the channel length is decreased, using conventional bulk materials such as silicon as the channel. Recently, two-dimensional semiconducting materials1,2,3,4,5,6,7 have emerged as promising candidates to replace silicon, as they can maintain excellent device electrostatics even at much reduced channel lengths. The second, more severe, challenge is that the supply voltage can no longer be scaled down by the same factor as the transistor dimensions because of the fundamental thermionic limitation of the steepness of turn-on characteristics, or subthreshold swing8,9. To enable scaling to continue without a power penalty, a different transistor mechanism is required to obtain subthermionic subthreshold swing, such as band-to-band tunnelling10,11,12,13,14,15,16. Here we demonstrate band-to-band tunnel field-effect transistors (tunnel-FETs), based on a two-dimensional semiconductor, that exhibit steep turn-on; subthreshold swing is a minimum of 3.9 millivolts per decade and an average of 31.1 millivolts per decade for four decades of drain current at room temperature. By using highly doped germanium as the source and atomically thin molybdenum disulfide as the channel, a vertical heterostructure is built with excellent electrostatics, a strain-free heterointerface, a low tunnelling barrier, and a large tunnelling area. Our atomically thin and layered semiconducting-channel tunnel-FET (ATLAS-TFET) is the only planar architecture tunnel-FET to achieve subthermionic subthreshold swing over four decades of drain current, as recommended in ref. 17, and is also the only tunnel-FET (in any architecture) to achieve this at a low power-supply voltage of 0.1 volts. Our device is at present the thinnest-channel subthermionic transistor, and has the potential to open up new avenues for ultra-dense and low-power integrated circuits, as well as for ultra-sensitive biosensors and gas sensors18,19,20,21.