Transconductance Amplification in Dirac‐Source Field‐Effect Transistors Enabled by Graphene/Nanotube Hereojunctions

Abstract

Steep‐slope devices are predicted to provide excellent quality for analog integrated circuit applications due to their high transconductance efficiency (gm/Ids) breaking the metal‐oxide‐semiconductor field‐effect transistor limit (38.5 V−1). The potential advantage of a Dirac‐source FET (DSFET) as an analog transistor is explored based on a graphene/carbon nanotube (CNT) heterojunction. A high gm/Ids beyond 38.5 V−1 over four decades of current is experimentally demonstrated in an individual CNT‐based DSFET, reaching a peak value of 66 V−1, which is a new record for all reported transistors. Importantly, this high gm/Ids extends beyond the subthreshold region and leads to transconductance amplification in the overthreshold region. The best peak transconductance at a low bias of −0.1 V exceeds 20 µS per tube, which has approximately threefold improvement over that of a normal CNT FET with a shorter gate length. Outperforming other advanced devices, the extended high transconductance efficiency greatly promotes DSFET competitiveness in the high‐precision analog field.

van der Waals Contact for Two-Dimensional Transition Metal Dichalcogenides

“…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).…”