Abstract
In a continuous search for the energy-efficient electronic switches, a great attention is focused on tunnel field-effect transistors (TFETs) demonstrating an abrupt dependence of the source-drain current on the gate voltage. Among all TFETs, those based on one-dimensional (1D) semiconductors exhibit the steepest current switching due to the singular density of states near the band edges, though the current in 1D structures is pretty low. In this paper, we propose a TFET based on 2D graphene bilayer which demonstrates a record steep subthreshold slope enabled by van Hove singularities in the density of states near the edges of conduction and valence bands. Our simulations show the accessibility of 3.5 × 104 ON/OFF current ratio with 150 mV gate voltage swing, and a maximum subthreshold slope of (20 μV/dec)−1 just above the threshold. The high ON-state current of 0.8 mA/μm is enabled by a narrow (~0.3 eV) extrinsic band gap, while the smallness of the leakage current is due to an all-electrical doping of the source and drain contacts which suppresses the band tailing and trap-assisted tunneling.
Highlights
For graphene electronic devices started a new chapter in the experimental studies of low-energy spectrum of bilayer, and the van Hove singularities[27,28] but even tinier features of carrier spectrum[29] were clearly revealed
In our paper we show that the van Hove singularity results in a steep, linear dependence of the GBL Tunnel FETs (TFETs) current on the gate voltage above the threshold, which was attributed previously just to the TFETs based on one-dimensional materials[5,8,30,31,32]
We have proposed and substantiated the operation of a graphene bilayer TFET exploiting the van Hove singularities in the density of states near the band edges
Summary
For graphene electronic devices started a new chapter in the experimental studies of low-energy spectrum of bilayer, and the van Hove singularities[27,28] but even tinier features of carrier spectrum[29] were clearly revealed. A number of GBL transistors have been proposed[33,34,35], including the TFETs36, our structure possesses a unique feature that allows one to exploit the density-of-states effect for tunneling. This feature is electrical doping of source and drain contacts instead of chemical one. This suppresses the band tailing induced by random dopants[37] and minimizes the leakage currents through defect states[38]. Apart from reducing the leakage, this adds the possibility to electrically reconfigure the device between n- and p-types
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