Mid-Wave Infrared Photoconductors Based on Black Phosphorus-Arsenic Alloys

Abstract

Black phosphorus (b-P) and more recently black phosphorus-arsenic alloys (b-PAs) are candidate 2D materials for the detection of mid-wave and potentially long-wave infrared radiation. However, studies to date have utilized laser-based measurements to extract device performance and the responsivity of these detectors. As such, their performance under thermal radiation and spectral response has not been fully characterized. Here, we perform a systematic investigation of gated-photoconductors based on b-PAs alloys as a function of thickness over the composition range of 0-91% As. Infrared transmission and reflection measurements are performed to determine the bandgap of the various compositions. The spectrally resolved photoresponse for various compositions in this material system is investigated to confirm absorption measurements, and we find that the cutoff wavelength can be tuned from 3.9 to 4.6 μm over the studied compositional range. In addition, we investigated the temperature-dependent photoresponse and performed calibrated responsivity measurements using blackbody flood illumination. Notably, we find that the specific detectivity (D*) can be optimized by adjusting the thickness of the b-P/b-PAs layer to maximize absorption and minimize dark current. We obtain a peak D* of 6 × 10 cm Hz W and 2.4 × 10 cm Hz W for pure b-P and b-PAs (91% As), respectively, at room temperature, which is an order of magnitude higher than commercially available mid-wave infrared detectors operating at room temperature.

Recent advances in low‐dimensional semiconductor nanomaterials and their applications in high‐performance photodetectors

“…The best example is the arsenic phosphorus alloy. B‐As x P 1‐x ( x = 0‐0.83) with adjustable composition enables bandgap and optical properties can be adjusted (Figure B) . The alloy (B‐As 0.83 P 0.17 ) with the largest composition of As atoms has a bandgap of 0.15 eV, which pushes the spectral range of the photovoltaic device to the farther infrared (IR) region (medium wave IR band).…”

“…D, Responsivity of B‐P device as a function of polarizer angle. Reproduced with permission . Copyright 2017, American Chemical Society.…”

“…The bandgap of B‐P can be tuned from 1.5 to 0.3 eV as the thickness changes, and the bandgap of B‐AsP can vary from 0.3 to 0.15 eV as the composition changes. Moreover, they have excellent anisotropy and have new application potential in the field of polarized light detection . Studies on B‐P have shown that B‐P has good optoelectronic properties in the visible to near‐IR (NIR) and even mid‐infrared (MIR) regions .…”

“…B‐P is a typical representative of materials with strong anisotropy. Significant polarization effects were shown in both B‐P and B‐AsP . PDs measurements indicate that the polarized light response extinction ratio is greater than 100 times.…”

“…And, this effect exists in a wide spectral range. Figure D shows the responsiveness of the B‐P device as a function of the angle of the polarizer, with a very pronounced polarization effect . Figure E is photocurrent maps of a B‐P photodetector with different light‐polarization angles, showing angle‐dependent photocurrent.…”