Tunable Quantum Tunneling through a Graphene/Bi₂Se₃ Heterointerface for the Hybrid Photodetection Mechanism

Abstract

Graphene-based van der Waals heterostructures are promising building blocks for broadband photodetection because of the gapless nature of graphene. However, their performance is mostly limited by the inevitable trade-off between low dark current and photocurrent generation. Here, we demonstrate a hybrid photodetection mode based on the photogating effect coupled with the photovoltaic effect via tunable quantum tunneling through the unique graphene/Bi 2 Se 3 heterointerface. The tunneling junction formed between the semimetallic graphene and the topologically insulating Bi 2 Se 3 exhibits asymmetric rectifying and hysteretic current–voltage characteristics, which significantly suppresses the dark current and enhances the photocurrent. The photocurrent-to-dark current ratio increases by about a factor of 10 with the electrical tuning of tunneling resistance for efficient light detection covering the major photonic spectral band from the visible to the mid-infrared ranges. Our findings provide a novel concept of using tunable quantum tunneling for highly sensitive broadband photodetection in mixed-dimensional van der Waals heterostructures.

Highly Sensitive MoS2 Photodetectors Enabled with a Dry-Transferred Transparent Carbon Nanotube Electrode

“…As we suggested earlier, the charge transport at reverse bias might be dominated by tunneling. Thus, we adopted direct tunneling (DT) and FNT models − to fit the I – V curves at reverse bias. DT and FNT are expressed using the following equations ln ( I D T V 2 ) = A q 2 m 0 normalΦ normalB h 2 d ln ( 1 V ) − 4 π d 2 m * normalΦ normalB h ln ( I F N T V 2 ) = ln ( A q 3 m 0 8 π h Φ B d 2 m * ) − 8 π d 2 m * normalΦ …”

“…As we suggested earlier, the charge transport at reverse bias might be dominated by tunneling. Thus, we adopted direct tunneling (DT) and FNT models − to fit the I – V curves at reverse bias. DT and FNT are expressed using the following equations where A , q , m 0 , Φ B , h , d , and m *­(0.45 m 0 ) are the junction area, elementary charge, free electron mass, barrier height, Planck constant, the thickness of MoS 2 flake, and effective electron mass, respectively.…”

“…The shift in the origin of charge carrier injection with the variation in the voltage magnitude has also been observed elsewhere. , The minimum transition voltage from DT to the FNT is around 0.28 V. In addition, the barrier height for the FNT was calculated to be ∼0.75 eV by taking the slope value extracted from the fitting result. The FNT is known to make a great contribution to the total current when the barrier height and width are small under high bias voltages. − …”

Gate-Tunable Helical Currents in Commensurate Topological Insulator/Graphene Heterostructures

“…Recently, attention has been directed toward coupling a graphene layer to the 2D surface of a three-dimensional topological insulator (3DTI). , The proximity of a 3DTI to graphene can induce sizable SOC and correspondingly spin textures in graphene, − with the further possibility of inducing Dirac states with very low Fermi velocity, in which interaction effects are predicted to be greatly enhanced . Of particular relevance is the tetradymite class of 3DTIs, which comprises bismuth chalcogenides like Bi 2 Se 3 , Bi 2 Te 3 , and Bi 2 Te 2 Se (BTS), because the lattice constants of their (111) surfaces have only a small mismatch with graphene, in stark contrast to large mismatches of for the transition-metal dichalcogenides on graphene.…”

Hybrid Photodetection Mechanisms Tuned with Tunneling

“…Among them, the photovoltaic effect is beneficial for fast photoresponse [13] and low power operation while the photogating effect is useful for high optical gain [14]. Very recently, it has been reported that this vdW heterojunction is a very suitable platform to study new 1 Hoon Hahn Yoon, Henry A. Fernandez, Fedor Nigmatulin, Faisal Ahmed, Xiaoqi Cui, Xueyin Bai, Diao Li, Mingde Du, Harri Lipsanen, Zhipei Sun are with the Department of Electronics and Nanoengineering, Aalto University, Fi-00076 Aalto, Finland (corresponding author: Hoon Hahn Yoon, email: hoonhahn.yoon@aalto.fi) photodetection mechanisms such as switchable [15], [16], hybrid [17], [18], negative [19], [20], and anti-ambipolar [21], [22] photoresponses. Based on vdW heterojunctions, a single dominant photodetection mechanism can be switched from one to another [15], [16] for multimode optoelectronics and its logic or neuromorphic computing applications, which is readily achievable by the engineering of band alignment or bending.…”