A Steep-Slope Transistor Combining Phase-Change and Band-to-Band-Tunneling to Achieve a sub-Unity Body Factor

Abstract

Steep-slope transistors allow to scale down the supply voltage and the energy per computed bit of information as compared to conventional field-effect transistors (FETs), due to their sub-60 mV/decade subthreshold swing at room temperature. Currently pursued approaches to achieve such a subthermionic subthreshold swing consist in alternative carrier injection mechanisms, like quantum mechanical band-to-band tunneling (BTBT) in Tunnel FETs or abrupt phase-change in metal-insulator transition (MIT) devices. The strengths of the BTBT and MIT have been combined in a hybrid device architecture called phase-change tunnel FET (PC-TFET), in which the abrupt MIT in vanadium dioxide (VO2) lowers the subthreshold swing of strained-silicon nanowire TFETs. In this work, we demonstrate that the principle underlying the low swing in the PC-TFET relates to a sub-unity body factor achieved by an internal differential gate voltage amplification. We study the effect of temperature on the switching ratio and the swing of the PC-TFET, reporting values as low as 4.0 mV/decade at 25 °C, 7.8 mV/decade at 45 °C. We discuss how the unique characteristics of the PC-TFET open new perspectives, beyond FETs and other steep-slope transistors, for low power electronics, analog circuits and neuromorphic computing.

Electronic structure of metallic and insulating phases of vanadium dioxide and its oxide alloys

“…Pure vanadium dioxide (VO 2 ) has two phases; below 340 K it has the monoclinic or M 1 phase with a band gap, whereas above 340 K it has the metallic rutile form, called the R phase [1][2][3]. The phase transition is fully reversible so that it is a promising material for various applications [4] such as smart windows [5], optical [6] or rf switches [7,8], and as a component of steep slope transistors [9][10][11]. Although the structural change at 340 K has been heavily studied, the electronic structures and especially the magnetic ground states of both R and M 1 phases are still debated [1,3,12].…”

A new approach to the fabrication of VO2 nanoswitches with ultra-low energy consumption

“…It is a wellknown fact that, in a VO 2 material exhibiting a pronounced T-MIT, the application of an electric field to the material in the insulating state also induces an MIT, most commonly referred to as an electrically-triggered MIT, without specifying the actual mechanism of this phase transition. [19][20][21][22][23][24][25][26][27][28][29][30][31][32] In the literature, the precise understanding of the electrically-triggered MIT mechanism is still disputable. 20,22,24 Several competing models explaining the MIT mechanism were proposed, and these are: the Joule heating model ,23,25 the electric-fieldinduced breakdown model 29,31,33 and the carrier injection model.…”

Nano-Particle VO2 Insulator-Metal Transition Field-Effect Switch with 42 mV/decade Sub-Threshold Slope

“…Recently, there has been an increased interest in developing high energy efficiency electronic switches using transition metal dichalcogenides [8] and IMT materials [9,10]. The grain size in polycrystalline VO 2 affects the IMT temperature as discussed in [11].…”