Mid-infrared time-resolved photoconduction in black phosphorus

Abstract

Black phosphorus has attracted interest as a material for use in optoelectronic devices due to many favorable properties such as a high carrier mobility, field-effect, and a direct bandgap that can range from 0.3 eV in its bulk crystalline form to 2 eV for a single atomic layer. The low bandgap energy for bulk black phosphorus allows for direct transition photoabsorption that enables detection of light out to mid-infrared frequencies. In this work we characterize the room temperature optical response of a black phosphorus photoconductive detector at wavelengths ranging from 1.56 $\mu$m to 3.75 $\mu$m. Pulsed autocorrelation measurements in the near-infrared regime reveal a strong, sub-linear photocurrent nonlinearity with a response time of 1 ns, indicating that gigahertz electrical bandwidth is feasible. Time resolved photoconduction measurements covering near- and mid-infrared frequencies show a fast 65 ps rise time, followed by a carrier relaxation with a time scale that matches the intrinsic limit determined by autocorrelation. The sublinear photoresponse is shown to be caused by a reduction in the carrier relaxation time as more energy is absorbed in the black phosphorus flake and is well described by a carrier recombination model that is nonlinear with excess carrier density. The device exhibits a measured noise-equivalent power of 530 pW/$\sqrt{\text{Hz}}$ which is the expected value for Johnson noise limited performance. The fast and sensitive room temperature photoresponse demonstrates that black phosphorus is a promising new material for mid-infrared optoelectronics.

arXiv comment18 pages, 6 figures

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Cited by in corpus (6)

• The Optical Properties and Plasmonics of Anisotropic 2-Dimensional Materials
• Accessing the anisotropic non-thermal phonon populations in black phosphorus
• Monolayer black phosphorus by sequential wet-chemical surface oxidation
• Sub-ns intrinsic response time of PbS nanocrystal IR-photodetectors
• Probing the Free-carrier Absorption in Multi-Layer Black Phosphorus
• Low-frequency interlayer phonon dynamics and photoinduced terahertz absorption in black phosphorus