Atomically thin van der Waals tunnel field-effect transistors and its potential for applications

Abstract

Power dissipation is a crucial problem as the packing density of transistors increases in modern integrated circuits. Tunnel field-effect transistors (TFETs), which have high energy filtering provided by band-to-band tunneling (BTBT), have been proposed as an alternative electronics architecture to decrease the energy loss in bias operation and to achieve steep switching at room temperature. Very recently, the BTBT behavior has been demonstrated in van der Waals heterostructures by using unintentionally doped semiconductors. The reason of the BTBT formation is attributed to a significant band bending near the heterointerface, resulting in carrier accumulations. In this work, to investigate charge transport in type-III transistors, we adopted the same band-bending concept to fabricate van der Waals BP/MoS 2 heterostructures. Through analyzing the temperature dependence of their electrical properties, we carefully ruled out the contribution of metal-semiconductor contact resistances and improved our understanding of carrier injection in 2D type-III transistors. The BP/MoS 2 heterostructures showed both negative differential resistance and 1/f 2 current fluctuations, strongly demonstrating the BTBT operation. Finally, we also designed a TFET based on this heterostructure with an ionic liquid gate, and this TFET demonstrated an subthreshold slope can successfully surmount the thermal limit of 60 mV/decade. This work improves our understanding of charge transport in such layered heterostructures and helps to improve the energy efficiency of next-generation nanoscale electronics.

Probing Charge Transport Difference in Parallel and Vertical Layered Electronics with Thin Graphite Source/Drain Contacts

“…Analysis of I ds − V ds characteristics of electronics at room temperature alone cannot provide a complete understanding of charge transport or elucidate the microscopic nature of inherent resistance formation 31,32 . Therefore, investigations of temperature dependence were also carried out.…”

Emerging Opportunities for Electrostatic Control in Atomically Thin Devices

“…A relatively sharp anti-ambipolar peak occurs in atomically thin SnS 2 –WSe 2 devices , with an impressively high PVR up to 10 4 but a 40 V operating window . An N-shaped anti-ambipolar response with a peak voltage near 0 V and a PVR of 10 5 for negative gate bias but <10 1 for positive gate bias was reported for the BP–WSe 2 system, while low-voltage operation of an N-shaped anti-ambipolar response with peaks near 1 V, PVRs of 10 2 , and a less than 3 V operating window has been reported in MoS 2 –BP devices using a semivertical geometry or an ionic-liquid gate . Further control of the anti-ambipolar response, including tuning of the peak position has been achieved using electrostatic approaches and optical pulsing.…”

“…More interestingly, the electrostatic control is strong enough to achieve reversal of the rectification direction as seen in MoS 2 –WSe 2 , , WSe 2 –BP, , MoSe 2 –WSe 2 , ReS 2 –MoTe 2 , WSe 2 –MoSe 2 , and WSe 2 –GeSe heterojunctions. Additionally, gate-tunable Zener diodes have been implemented using MoS 2 –BP heterojunctions, , and in the case of BP–InSe heterojunctions, high electrostatic doping resulted in a Zener diode response, while low electrostatic doping resulted in an avalanche response that is useful for impact ionization FETs …”

“…Additional 2D–2D heterojunctions including MoS 2 –BP, ,,,, MoS 2 –GaTe, MoS 2 –MoTe 2 , ,, MoS 2 –WSe 2 , ,, SnS 2 –WSe 2 , , and BP–WSe 2 have also exhibited anti-ambipolar transistor responses. A relatively sharp anti-ambipolar peak occurs in atomically thin SnS 2 –WSe 2 devices , with an impressively high PVR up to 10 4 but a 40 V operating window .…”

Facile and Reversible Carrier-Type Manipulation of Layered MoTe2 Toward Long-Term Stable Electronics

“…Because of their favorable properties, such as atomic thickness, lack of dangling bonds, high surface stability, and successful demonstration of nano/microdevices with fascinating features, layered two-dimensional (2D) materials, including MoS 2 , − WSe 2 , − ReSe 2 , − MoTe 2 , − and InSe, , have been attracting tremendous interest for use in 2D material-based optoelectronic devices over the past few decades. Among these layered 2D materials, MoTe 2 , known for its energy gap of 1.1 eV (close to that of Si) and stable physical/chemical characteristics, − is regarded as a promising candidate to develop next-generation opto/electronics with excellent carrier mobility, durability, and high compatibility with current semiconductor manufacturing processes.…”