Efficient light generation from enhanced inelastic electron tunnelling


Light emission from biased tunnel junctions has recently gained much attention owing to its unique potential to create ultracompact optical sources with terahertz modulation bandwidth1,2,3,4,5. The emission originates from an inelastic electron tunnelling process in which electronic energy is transferred to surface plasmon polaritons and subsequently converted to radiation photons by an optical antenna. Because most of the electrons tunnel elastically, the emission efficiency is typically about 10−5–10−4. Here, we demonstrate efficient light generation from enhanced inelastic tunnelling using nanocrystals assembled into metal–insulator–metal junctions. The colour of the emitted light is determined by the optical antenna and thus can be tuned by the geometry of the junction structures. The efficiency of far-field free-space light generation reaches ~2%, showing an improvement of two orders of magnitude over previous work3,4. This brings on-chip ultrafast and ultracompact light sources one step closer to reality.

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Fig. 1: Light emission from an electrically driven optical antenna engineered at the atomic level.
Fig. 2: Investigation of Ag square-prism-based tunnel junctions.
Fig. 3: Numerical and experimental study of Ag nanobar-based tunnel junctions.
Fig. 4: Silver nanobar-based tunnel junction with optimized EQE.


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This work is financially supported by the Defense Advanced Research Projects Agency (DARPA) Microsystems Technology Office (W911NF-16-2-0156). We thank J. Conway for suggestions.

Author information




Z.L. conceived the project. H.Q. and S.-W.H. designed the structures. H.Q. performed the experiments. S.-W.H. and K.G. prepared and characterized the Ag nanocrystals. H.Q. performed the theoretical work. H.Q., S.-W.H., K.G., C.T.R., J.Z., D.L., A.R.T. and Z.L. wrote the manuscript. All authors analysed the data and contributed to the discussion. A.R.T. and Z.L. supervised the research.

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Correspondence to Andrea R. Tao or Zhaowei Liu.

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Qian, H., Hsu, SW., Gurunatha, K. et al. Efficient light generation from enhanced inelastic electron tunnelling. Nature Photon 12, 485–488 (2018). https://doi.org/10.1038/s41566-018-0216-2

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