Reducing ambipolar off-state leakage currents in III-V vertical nanowire tunnel FETs using gate-drain underlap

Research output: Contribution to journalArticle

Abstract

Tunnel Field-Effect Transistors (TFETs) are an emerging alternative to CMOS for ultralow power and neuromorphic applications. The off current (Ioff) and, hence, the subthreshold swing (S) in these devices are limited by ambipolarity, which degrades its capabilities in complementary circuits. Here, we investigate experimentally vertical InAs/InGaAsSb/GaSb nanowire TFETs with gate-drain underlap as a potential solution to avoid ambipolarity and study the temperature dependence of the tunneling current. We compare two different TFET designs, one with an underlap between the gate and drain and the other with an overlap. The introduction of a 25-nm-long underlap region reduced the minimum achievable current Imin from 92 pA/μm to 23 pA/μm by suppressing the ambipolarity and simultaneously improved the minimum S at room temperature from 46 mV/dec to 41 mV/dec at Vds = 0.1 V. We also observe a reduction in the measured on current (Ion) from 0.1 μA/μm in the overlapped device to 0.01 μA/μm in the underlapped device at a drain bias (Vds) = 0.1 V and Ioff = 1 nA/μm. Temperature dependent measurements reveal a potential barrier at the drain junction due to the ungated region at the underlap. We determine a barrier height of 63 meV at Vds = 0.1 V based on thermionic emission combined with a ballistic transport model. Thus, we conclude that gate placement on the drain side is crucial to obtain the low off-currents in TFETs required for ultralow power electronic applications but that the trade-off between Ion and Ioff has to be considered.

Details

Authors
Organisations
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Nano Technology
Original languageEnglish
Article number143505
JournalApplied Physics Letters
Volume115
Issue number14
Publication statusPublished - 2019 Oct 1
Publication categoryResearch
Peer-reviewedYes

Related infrastructure

View all (1)