Gate-Tunable Resonant Tunneling in Double Bilayer Graphene Heterostructures

Fallahazad, Babak; Lee, Kayoung; Kang, Sangwoo; Xue, Jiamin; Larentis, Stefano; Corbet, Chris M.; Kim, Kyounghwan; Movva, Hema C. P.; Taniguchi, Takashi; Watanabe, Kenji; Register, Leonard F.; Tutuc, Emanuel

doi:10.1021/nl503756y

Cited by 183 publications

(179 citation statements)

References 27 publications

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“…Thinner barrier devices show a finite linear tunnel current at low biases and a roughly exponential dependence of the low bias resistance with d, complying with standard quantum mechanical tunneling, in agreement with previous reports 9,12 . However, in relatively thicker barrier devices, we find signatures of Coulomb blockade and single electron tunneling events.…”

supporting

confidence: 91%

“…The voltage range probed is believed to be below the Fowler-Nordheim regime, where the barrier is essentially triangular, due to a very high applied bias 8 . In recent studies, NDR signatures were observed in single and bilayer graphene based heterostructures, which were attributed to resonant tunneling via momentum conservation when the energy bands of the top and bottom graphene layers were aligned 11,12 . However, we find sim-ilar I-V curves in simple M-I-M junctions here, albeit with peak to valley ratios lower than in graphene based devices.…”

mentioning

confidence: 99%

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Evidence for Defect-Mediated Tunneling in Hexagonal Boron Nitride-Based Junctions

et al. 2015

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We investigate tunneling in metal-insulator-metal junctions employing few atomic layers of hexagonal boron nitride (hBN) as the insulating barrier. While the low-bias tunnel resistance increases nearly exponentially with barrier thickness, subtle features are seen in the current-voltage curves, indicating marked influence of the intrinsic defects present in the hBN insulator on the tunneling transport. In particular, single electron charging events are observed, which are more evident in thicker-barrier devices where direct tunneling is substantially low. Furthermore, we find that annealing the devices modifies the defect states and hence the tunneling signatures.Van der Waals heterostructures, where layered stacks of two dimensional materials are embedded in precisely desired patterns, have gained immense attention in recent times 1,2 . Such tailor-made structures of graphene, hexagonal boron nitride (hBN), metal dichalcogenides and other 2D materials offer exotic device geometries to explore new physics. Tunnel junctions with an atomically thin insulator barrier sandwiched between atomic layers of 2D materials form an interesting structure in this respect. In conventional two dimensional semiconductor double layer structures, tunneling has shown remarkable features, including resonant tunneling, Coulomb correlations at high magnetic fields and Landau-level spectroscopy 3-6 . In the regime of 2D layered materials, hBN with a band gap of ∼ 5.9 eV 7 is an ideal candidate for an insulating barrier 8 . Recent studies on heterostructures with single and bilayer graphene as electrodes and hBN as the insulator have shown interesting features, including a very strong negative differential resistance (NDR) 9-12 . In all of these transport studies hBN is assumed to be a benign element. However, from a materials perspective there have been extensive efforts to understand the underlying structure and defect mechanisms in thin layers of hBN, which can have important consequences on electrical transport 13-15 . Here we present detailed tunneling transport measurements on simple junctions consisting of metal or graphite electrodes separated by a thin hBN layer. Our results demonstrate that the hBN insulator can yield unexpected transport signatures suggestive of defect-mediated tunneling processes.In a conventional metal-insulator-metal (M-I-M) junction, the tunnel current-voltage characteristic (I-V ) is linear at low biases, with the tunneling resistance inversely proportional to sample area and exponentially dependent on the barrier thickness d. Our studies show that the I-V with hBN as the barrier is distinct from such a simple behavior in various respects. Thinner barrier devices show a finite linear tunnel current at low biases and a roughly exponential dependence of the low bias resistance with d, complying with standard quantum mechanical tunneling, in agreement with previous reports 9,12 . However, in relatively thicker barrier devices, h--BN

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confidence: 91%

mentioning

confidence: 99%

Evidence for Defect-Mediated Tunneling in Hexagonal Boron Nitride-Based Junctions

et al. 2015

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“…Resonate tunneling current and negative differential resistance (NDR) have been observed in graphene‐based heterostructure TFETs, including monolayer and bilayer graphene separated by BN25, 26, 27, 28, 29, 30 or TMDs 6, 31. However, due to the absence of a bandgap, graphene‐based TFETs are unable to obtain a high on/off ratio of the current.…”

Section: Introductionmentioning

confidence: 99%

Independent Band Modulation in 2D van der Waals Heterostructures via a Novel Device Architecture

et al. 2018

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Benefiting from the technique of vertically stacking 2D layered materials (2DLMs), an advanced novel device architecture based on a top‐gated MoS2/WSe2 van der Waals (vdWs) heterostructure is designed. By adopting a self‐aligned metal screening layer (Pd) to the WSe2 channel, a fixed p‐doped state of the WSe2 as well as an independent doping control of the MoS2 channel can be achieved, thus guaranteeing an effective energy‐band offset modulation and large through current. In such a device, under specific top‐gate voltages, a sharp PN junction forms at the edge of the Pd layer and can be effectively manipulated. By varying top‐gate voltages, the device can be operated under both quasi‐Esaki diode and unipolar‐Zener diode modes with tunable current modulations. A maximum gate‐coupling efficiency as high as ≈90% and a subthreshold swing smaller than 60 mV dec−1 can be achieved under the band‐to‐band tunneling regime. The superiority of the proposed device architecture is also confirmed by comparison with a traditional heterostructure device. This work demonstrates the feasibility of a new device structure based on vdWs heterostructures and its potential in future low‐power electronic and optoelectronic device applications.

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“…2, 31, 32) and bilayer graphene (Refs. 33,34) as presented in the thesis have been observed in the time since this work began. Therefore, it is single-particle e ects that will be the focus of the thesis, and beyond this section many-body e ects will not be considered further.…”

Section: Many-body E Ects and Excitonic Condensatesmentioning

confidence: 83%