Abstract
Lately rediscovered orthorhombic black phosphorus (BP) exhibits promising properties for near- and mid-infrared optoelectronics. Although recent electrical measurements indicate that a vertical electric field can effectively reduce its transport bandgap, the impact of the electric field on light-matter interaction remains unclear. Here we show that a vertical electric field can dynamically extend the photoresponse in a 5 nm-thick BP photodetector from 3.7 to beyond 7.7 μm, leveraging the Stark effect. We further demonstrate that such a widely tunable BP photodetector exhibits a peak extrinsic photo-responsivity of 518, 30, and 2.2 mA W−1 at 3.4, 5, and 7.7 μm, respectively, at 77 K. Furthermore, the extracted photo-carrier lifetime indicates a potential operational speed of 1.3 GHz. Our work not only demonstrates the potential of BP as an alternative mid-infrared material with broad optical tunability but also may enable the compact, integrated on-chip high-speed mid-infrared photodetectors, modulators, and spectrometers.
Highlights
Rediscovered orthorhombic black phosphorus (BP) exhibits promising properties for near- and mid-infrared optoelectronics
We demonstrate widely tunable mid-IR photodetectors operating up to 7.7 μm based on a hexagonal boron nitride/BP/hBN-sandwiched heterostructure
The schematic and optical images of the BP photodetector based on a dual-gate transistor structure are shown in Fig. 1a, b, respectively
Summary
Rediscovered orthorhombic black phosphorus (BP) exhibits promising properties for near- and mid-infrared optoelectronics. If the light-BP interaction leveraging interband transitions can be dynamically tuned within a wide spectral range in mid-IR, optical devices beyond photodetectors, such as on-chip high-speed mid-IR optical modulators and spectrometers, may be built based on this concept of dynamic response tuning. Recent transport studies in the BP thin film show that a vertical electric field can effectively reduce its transport bandgap by shifting its band edge energies[23,24,25] Such strong tuning of transport bandgap has been observed in few-layer transition metal dichalcogenides[26]. The widely tunable photoresponse combined with theoretical calculations show the promising future of BP thin film as an alternative and high-quality material for midIR photonics especially for integrated photonic systems
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