Dirac-source diode with sub-unity ideality factor

Abstract

An increase in power consumption necessitates a low-power circuit technology to extend Moore’s law. Low-power transistors, such as tunnel field-effect transistors (TFETs), negative-capacitance field-effect transistors (NC-FETs), and Dirac-source field-effect transistors (DS-FETs), have been realised to break the thermionic limit of the subthreshold swing (SS). However, a low-power rectifier, able to overcome the thermionic limit of an ideality factor (η) of 1 at room temperature, has not been proposed yet. In this study, we have realised a DS diode based on graphene/MoS2/graphite van der Waals heterostructures, which exhibits a steep-slope characteristic curve, by exploiting the linear density of states (DOSs) of graphene. For the developed DS diode, we obtained η < 1 for more than four decades of drain current (ηave_4dec < 1) with a minimum value of 0.8, and a rectifying ratio exceeding 108. The realisation of a DS diode represents an additional step towards the development of low-power electronic circuits.

van der Waals Contact for Two-Dimensional Transition Metal Dichalcogenides

“…Notably, a Dirac source diode with η < 1 spanning over four decades is demonstrated in graphene/MoS 2 /graphite vdW heterostructures (Figure 9g,h). 74 Compared to tunneling field-effect transistors (TFETs) that leverage the bandgap of the source to filter thermionic carriers, the gapless nature of graphene still allows for high-energy carrier leakage. 75 This characteristic may impose limitations on the minimum achievable SS with this contact strategy.…”

“…Besides applications in low-power transistors, graphene is also utilized as a Dirac source in diodes to surpass the thermionic limit of an ideality factor η (1 at room temperature). Notably, a Dirac source diode with η < 1 spanning over four decades is demonstrated in graphene/MoS 2 /graphite vdW heterostructures (Figure g,h) . Compared to tunneling field-effect transistors (TFETs) that leverage the bandgap of the source to filter thermionic carriers, the gapless nature of graphene still allows for high-energy carrier leakage .…”

“…In addition to serving as standard source–drain contacts in a conventional transistor, graphene also plays the role of an energy filter in emerging Dirac source field-effect transistors (DSFETs) that exhibit subthermionic switching performance with a subthreshold swing (SS) lower than 60 mV/decade at room temperature. − The pioneering demonstration of a DSFET is based on graphene-contacted carbon nanotube transistors, in which the narrower electron density n ( E ) distribution around the Fermi level of graphene is successfully exploited to reduce SS . This concept has been applied to 2D TMD transistors. , In a conventional transistor, the normal metallic source possesses a constant DOS, and n ( E ) follows a Boltzmann distribution with a long thermal tail above the Fermi level (Figure a).…”

“…The rectifying ratio of this device is larger than 10 8 . Panels g and h reproduced with permission from ref . Copyright 2022 Springer Nature.…”

Contact-engineered reconfigurable two-dimensional Schottky junction field-effect transistor with low leakage currents

“…Emerging reconfigurable technologies based on two-dimensional (2D) materials are expected to empower next-generation electronic devices with lower power consumption and higher expressive capability 1 – 5 . Different from conventional complementary metal-oxide semiconductor (CMOS) technologies, 2D-materials-based transistors show the dopant-free polarity control that the conduction mechanism reversibly switches between n-type and p-type operation modes under gate-voltage sweeps 6 – 8 .…”