Sustained Sub-60 mV/decade switching via the negative capacitance effect in MoS2 transistors

Felicia A. McGuire, Yuh Chen Lin, Katherine Price, G. Bruce Rayner, Sourabh Khandelwal, Sayeef Salahuddin, Aaron D. Franklin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

156 Citations (Scopus)

Abstract

It has been shown that a ferroelectric material integrated into the gate stack of a transistor can create an effective negative capacitance (NC) that allows the device to overcome "Boltzmann tyranny". While this switching below the thermal limit has been observed with Si-based NC field-effect transistors (NC-FETs), the adaptation to 2D materials would enable a device that is scalable in operating voltage as well as size. In this work, we demonstrate sustained sub-60 mV/dec switching, with a minimum subthreshold swing (SS) of 6.07 mV/dec (average of 8.03 mV/dec over 4 orders of magnitude in drain current), by incorporating hafnium zirconium oxide (HfZrO2 or HZO) ferroelectric into the gate stack of a MoS2 2D-FET. By first fabricating and characterizing metal-ferroelectric-metal capacitors, the MoS2 is able to be transferred directly on top and characterized with both a standard and a negative capacitance gate stack. The 2D NC-FET exhibited marked enhancement in low-voltage switching behavior compared to the 2D-FET on the same MoS2 channel, reducing the SS by 2 orders of magnitude. A maximum internal voltage gain of 28× was realized with 12 nm thick HZO. Several unique dependencies were observed, including threshold voltage (Vth) shifts in the 2D NC-FET (compared to the 2D-FET) that correlate with source/drain overlap capacitance and changes in HZO (ferroelectric) and HfO2 (dielectric) thicknesses. Remarkable sub-60 mV/dec switching was obtained from 2D NC-FETs of various sizes and gate stack thicknesses, demonstrating great potential for enabling size- and voltage-scalable transistors.

Original languageEnglish
Pages (from-to)4801-4806
Number of pages6
JournalNano Letters
Volume17
Issue number8
DOIs
Publication statusPublished - 9 Aug 2017

Keywords

  • negative capacitance
  • ferroelectric
  • MoS2
  • 2D
  • field-effect transistor
  • steep switching
  • HfZrO
  • HZO

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