Suppressing Ambipolar Current in UTFET by Auxiliary Gate
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RESEARCH PAPER
Suppressing Ambipolar Current in UTFET by Auxiliary Gate Kaveh Eyvazi1 • Mohammad Azim Karami1 Received: 14 March 2020 / Accepted: 14 September 2020 Ó Shiraz University 2020
Abstract In this paper, a new U-shaped channel tunneling-based field-effect transistor (UTFET) with auxiliary gate above drain is proposed. The ambipolar current in the proposed is investigated, in which simulation results show that ambipolar current takes place, due to drain-to-drain tunneling similar to gate-induced drain leakage in conventional MOSFETs. By drain depletion in auxiliary gate-based UTFET, electric field is reduced in ambipolar tunneling region, which causes tunneling barrier width to increase and the energy window of tunneling (DU) to decrease. As a result, two decades of reduction in the ambipolar current is achieved and ambipolar subthreshold swing (SSamb) is degraded by 24.8% in comparison with similar structure without auxiliary gate. Keywords Tunnel field-effect transistors Ambipolar current Depletion mode
1 Introduction By increasing the number of transistors per chip, reducing power consumption is among the essential requirements of electronic industry (Ionescu and Riel 2011). Reducing power consumption requires reducing the supply voltage and subthreshold leakage (Turkane and Kureshi 2016). Complementary metal–oxide–semiconductor (CMOS) transistors cannot show progressive performance due to limitation in supply voltage scaling and subthreshold swing limitation below 60 mV/dec at room temperature (Ionescu and Riel 2011), (Turkane and Kureshi 2016). In recent years, tunneling-based field-effect transistors (TFETs) emerged as alternatives for conventional MOSFETs due to lower leakage current and the possibility of reaching lower subthreshold swing (Boucart and Ionescu 2007). However, TFETs are constrained due to two fundamental challenges (Avci et al. 2015): low ON current and ambipolar behavior existence.
& Mohammad Azim Karami [email protected] Kaveh Eyvazi [email protected] 1
School of Electrical Engineering, Iran University of Science and Technology, Tehran 1684613114, Iran
The carrier injection mechanism of TFET is based on band-to-band tunneling (BTBT) phenomenon, in which electron tunnels from occupied valence band states of the source region into the unoccupied states of conduction band of the channel (Boucart and Ionescu 2007). The transmission probability of tunneling of charge carriers at source/channel junction increases with decrement in screening tunneling length. The small tunneling crosssectional area in conventional TFETs leads to ON current limitations (Kim 2012). In order to increase ON current, Z-Shaped TFET (ZS-TFET) (Imenabadi et al. 2017), T-shaped gate TFET (TG-TFET) (Li et al. 2017a, b), L-shaped gate and channel (LLTFET) (Abraham and James 2020) and U-shaped channel TFET (UTFET) with wider tunneling area are developed (Xie and Liu 2020), (Debnath et al. 2020). In addition, TFETs application is limited by ambipolar behavior (Avci et al. 2015). Ambipolar behavior occu
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