5934 IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 69, NO. 10, OCTOBER 2022 Tunneling FET Based on Monolayer Antimonene: The Role of Vacancy Hossein N. Niknezhad and Shoeib Babaee Touski Abstract — In this work, the electrical performance of 1 the antimonene TFET is investigated using nonequilibrium 2 Green’s function (NEGF) through a tight-binding approach. 3 In the following, the effect of atom vacancy on the electri- 4 cal behavior of the TFET is explored. The creation of the 5 mid-gap state due to the vacancy is shown using the local 6 density of states (LDOS) for the TFET and the density of 7 states (DOS) for a ribbon. Furthermore, the effects of these 8 mid-gap states on the ON-current, OFF-current, ON–OFF ratio, 9 and subthreshold swing (SS) are discussed. Finally, the 10 effect of the scaling in presence of vacancy is explored. 11 The results show that a small vacancy percentage declines 12 the SS while the variation of the ON–OFF ratio is negligible. 13 Index Terms— 2-D material, antimonene, nonequilibrium 14 Green’s function (NEGF), TFET, tight-binding, vacancy 15 defect. 16 I. I NTRODUCTION 17 I NTERNATIONAL Roadmap for Devices and Systems 18 recommends the 2-D materials as a promising channel 19 material for the next-generation transistors. The separation of 20 the single-layer graphene sheets with mechanical exfoliation 21 of graphite bulk paved the way for 2-D materials [1]. The 22 family of 2-D materials offers the full range of physical 23 properties, from the semimetallic property of graphene to 24 the semiconductor MoS 2 to the wide bandgap insulator of 25 hexagonal boron-nitride (h-BN). Since the birth of graphene 26 in 2004, the electronic community considers graphene as 27 a substitution for silicon [2]. However, the nature of the 28 zero bandgaps prevents graphene transistors from turning 29 off [3]. Of course, it is worth noting that the carbon nanotube 30 (1-D shape) can be used as a transistor channel [4]. MoS 2 is 31 another 2-D semiconductor that demonstrates potential com- 32 plement to graphene [5]. To build digital circuits on transparent 33 and flexible substrates, is also attractive, while its bandgap 34 is 1.8 eV [6], [7]. To prevent source tunneling to the drain 35 in the range of transistors on silicone shows advantages [8]. 36 Since 2004, many other 2-D materials have been discovered, 37 such as metal transition dichalcogenides (TMDs), h-BN, black 38 phosphorus (BP), or phosphorene. In 2014, BP successfully 39 Manuscript received 22 May 2022; revised 9 July 2022; accepted 12 August 2022. Date of publication 14 September 2022; date of current version 22 September 2022. The review of this article was arranged by Editor F. Schwierz. (Corresponding author: Shoeib Babaee Touski.) The authors are with the Department of Electrical Engineering, Hamedan University of Technology, Hamedan 65155, Iran (e-mail: touski@hut.ac.ir). Color versions of one or more figures in this article are available at https://doi.org/10.1109/TED.2022.3201782. Digital Object Identifier 10.1109/TED.2022.3201782 discovered the gap between graphene and TMDs. BP repre- 40 sents a layer-dependent bandgap that can be modulated from 41 0.3 (bulk) to 2.0 eV (single layer) [9]. Unfortunately, studies 42 have shown that BP is very unstable and decomposes easily 43 under light, so its application in electronics is also limited. 44 Antimonene (2-D allotrope of antimony) was first developed 45 experimentally in 2016 [10] and quickly gained popularity 46 over the next few years [11], [12], [13], [14]. In particular, 47 antimonene due to its semiconducting properties which have 48 been confirmed by experimental and theoretical results has 49 shown high potential in nanophotonics. A preliminary theoret- 50 ical study of antimonene was performed by Zhang et al. [15] 51 in 2015. Their studies show that the antimony bulk demon- 52 strates metallic properties even when reduced to only two 53 layers. However, a wide bandgap of 2.28 eV is predicted for 54 the antimonene monolayer. Further studies are reported smaller 55 bandgap values (0.76 and 1.55 eV) considering spin-orbit cou- 56 pling (SOC) [16]. Antimonene shows many properties along 57 with high stability [15], [17], such as high carrier mobility 58 (μ e = 630 and μ h = 1737 cm 2 /V · s). This monolayer 59 exhibits a high electric current [18], [19], which makes it 60 a promising material for the design of field-effect transistors 61 (FETs) [15], [20], [21], [22], [23], [24]. The moderate bandgap 62 of antimonene along with large carrier mobility makes this 63 material suitable for applications in MOSFETs [19]. 64 The scaling of the silicon transistors has led to the 65 improvement of the energy efficiency and reduced cost per 66 FET [25]. However, advanced nanoscale MOSFET technology 67 is faced with power consumption problems due to leakage 68 currents [26], [27]. The decrement of the power supply voltage 69 is proposed as a solution for the leakage current reduction. 70 The lower supply voltage is achieved by a lower subthreshold 71 swing (SS) that is limited to 60 mV/decade for conventional 72 FETs. TFET is proposed as one of the most promising 73 candidates for low-power switching devices due to the lower 74 SS below the 60 mV/decade at room temperature [26]. Unlike 75 conventional MOSFETs which are based on the thermionic 76 emission mechanism at the source, the current in TFET is 77 controlled by a band-to-band tunneling (BTBT) process that 78 electrons tunnels from the valence band of the source to the 79 conduction band in the channel [28]. 80 The 2-D materials have been widely studied as the channel 81 for TFET devices [29]. TMDs have been widely studied due to 82 the large bandgap and suitable electrical properties [30], [31]. 83 However, the relatively large effective mass and low mobility 84 of TMDs carriers have generally limited their application 85 for TFETs. In the following, BP is utilized as the channel 86 0018-9383 © 2022 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See https://www.ieee.org/publications/rights/index.html for more information. Authorized licensed use limited to: ULAKBIM UASL - DOKUZ EYLUL UNIVERSITESI. 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