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Exaggerated sensitivity in photodetectors with internal gain

Nature Photonics volume 15, page 714 (2021)Cite this article

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To the Editor — A growing number of reports on photodetection with low-dimensional materials have assumed that a photodetector with a high responsivity has a high sensitivity1,2,3,4,5,6,7. This misinterpretation stems from an incorrect calculation of the device noise in the presence of internal gain. Given the prevalence and significance of this mischaracterization, we believe it is imperative to promote the use of the appropriate noise formula to ensure the consistency and practical utility of the relevant literature.

Low-dimensional materials are an important frontier for novel photodetectors, and large internal gains have enabled the demonstration of high responsivities8. The current responsivity, defined as the photocurrent per optical power incident on the detector, is an indication of the internal gain of a detector. While internal gain is important to amplify the signal above the noise floor of the read-out electronics9, modest gains of 102 to 103 are sufficient to render the read-out noise inconsequential in most modern read-out electronics. In this regime, the detector is often shot noise-limited, implying that a further increase in gain will not yield any improvement in the device sensitivity, as we will show. Indeed, detector designs that simply maximize responsivity often result in low device speed or high dark current, both of which are actually detrimental to performance.

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Authors and Affiliations

  1. Department of Electrical and Computer Engineering, Northwestern University, Evanston, IL, USA

    Simone Bianconi & Hooman Mohseni

  2. Department of Materials Science and Engineering, Northwestern University, Evanston, IL, USA

    Lincoln J. Lauhon

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  1. Simone Bianconi
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  2. Lincoln J. Lauhon
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  3. Hooman Mohseni
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Correspondence to Hooman Mohseni.

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Bianconi, S., Lauhon, L.J. & Mohseni, H. Exaggerated sensitivity in photodetectors with internal gain. Nat. Photon. 15, 714 (2021). https://doi.org/10.1038/s41566-021-00843-6

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