The spectral response of common optoelectronic photodetectors is restricted by a cutoff wavelength limit λc that is related to the activation energy (or bandgap) of the semiconductor structure (or material) (Δ) through the relationship λc = hc/Δ. This spectral rule dominates device design and intrinsically limits the long-wavelength response of a semiconductor photodetector. Here, we report a new, long-wavelength photodetection principle based on a hot–cold hole energy transfer mechanism that overcomes this spectral limit. Hot carriers injected into a semiconductor structure interact with cold carriers and excite them to higher energy states. This enables a very long-wavelength infrared response. In our experiments, we observe a response up to 55 µm, which is tunable by varying the degree of hot-hole injection, for a GaAs/AlGaAs sample with Δ = 0.32 eV (equivalent to 3.9 µm in wavelength).
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This work was supported in part by the US Army Research Office (grant no. W911NF-12-2-0035), monitored by William W. Clark, and in part by the US National Science Foundation (grant no. ECCS-1232184, monitored by John M. Zavada). The University of Leeds acknowledges supports from the UK Engineering and Physical Sciences Research Council and E.H.L. from the European Research Council Advanced Grant ‘TOSCA’. Authors wish to dedicate this paper to the memory of Dr. H. C. Liu (H.C. as he was universally known). H.C. was an integral part of this work, and was inspirational to generations of researcher.
The authors declare no competing financial interests.
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Lao, YF., Perera, A., Li, L. et al. Tunable hot-carrier photodetection beyond the bandgap spectral limit. Nature Photon 8, 412–418 (2014). https://doi.org/10.1038/nphoton.2014.80
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