Resonant Light Emission from Graphene/Hexagonal Boron Nitride/Graphene Tunnel Junctions

Anna Kuzmina,Kenji Watanabe,Lukas Novotny,Patrick Back,Markus Parzefall,Achint Jain,Takashi Taniguchi

doi:10.1021/acs.nanolett.1c02913

Anna Kuzmina, Kenji Watanabe + Show 5 more

Open Access

https://doi.org/10.1021/acs.nanolett.1c02913

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Abstract

Single-layer graphene has many remarkable properties but does not lend itself as a material for light-emitting devices as a result of its lack of a band gap. This limitation can be overcome by a controlled stacking of graphene layers. Exploiting the unique Dirac cone band structure of graphene, we demonstrate twist-controlled resonant light emission from graphene/hexagonal boron nitride (h-BN)/graphene tunnel junctions. We observe light emission irrespective of the crystallographic alignment between the graphene electrodes. Nearly aligned devices exhibit pronounced resonant features in both optical and electrical characteristics that vanish rapidly for twist angles θ ≳3°. These experimental findings can be well-explained by a theoretical model in which the spectral photon emission peak is attributed to photon-assisted momentum conserving electron tunneling. The resonant peak in our aligned devices can be spectrally tuned within the near-infrared range by over 0.2 eV, making graphene/h-BN/graphene tunnel junctions potential candidates for on-chip optoelectronics.

Highlights

The unique electrical,[1] thermal,[2] and mechanical[3] properties of graphene have enabled the realization of novel nanoscale devices for integrated electronics and photonics.[4]
Electrically biased graphene can be heated to ∼3000 K, giving rise to blackbody radiation in the near-infrared and visible ranges.[9−12] The emission spectrum of these thermal sources can be shaped by the optical environment,[11,12] but the broad spectral response is not favorable for optoelectronic applications
When the two singlelayer graphene (SLG) flakes are separated by a thin insulator, like hexagonal boron nitride (h-BN), the band structure of each graphene layer remains unchanged

Summary

■ INTRODUCTION

The unique electrical,[1] thermal,[2] and mechanical[3] properties of graphene have enabled the realization of novel nanoscale devices for integrated electronics and photonics.[4]. The natural (ABstacked) bilayer graphene features a band gap, but its energy is too low for practical applications in the telecom or visible spectral range.[13] A twist between the two graphene layers alters the band structure and the optical properties of the system, as demonstrated by the observation of visible photoluminescence as a result of strongly bound excitons.[14] When the two singlelayer graphene (SLG) flakes are separated by a thin insulator, like hexagonal boron nitride (h-BN), the band structure of each graphene layer remains unchanged In this case, the mutual angular orientation between graphene layers defines the relative alignment of the Dirac cones in momentum space and, governs the electrical transport properties.[15] It has been predicted that plasmons in graphene/h-BN/graphene (Gr/hBN/Gr) heterostructures can be efficiently excited by electron tunneling.[16] Mid-infrared plasmons in these heterostructures have been experimentally verified using near-field microscopy.[17] the plasmon wavelength and the plasmon propagation length of visible and near-infrared graphene plasmons are extremely short, which results in thermal heating and hinders optoelectronic applications.

■ RESULTS AND DISCUSSION

■ CONCLUSION

■ ACKNOWLEDGMENTS

■ REFERENCES