Black phosphorus nanodevices at terahertz frequencies: Photodetectors and future challenges

Abstract

The discovery of graphene triggered a rapid rise of unexplored two-dimensional materials and heterostructures having optoelectronic and photonics properties that can be tailored on the nanoscale. Among these materials, black phosphorus (BP) has attracted a remarkable interest thanks to many favorable properties, such as high carrier mobility, in-plane anisotropy, the possibility to alter its transport via electrical gating and direct band-gap, that can be tuned by thickness from 0.3 eV (bulk crystalline) to 1.7 eV (single atomic layer). When integrated in a microscopic field effect transistor (FET), a few-layer BP flake can detect Terahertz (THz) frequency radiation. Remarkably, the in-plane crystalline anisotropy can be exploited to tailor the mechanisms that dominate the photoresponse; a BP-based field effect transistor can be engineered to act as a plasma-wave rectifier, a thermoelectric sensor or a thermal bolometer. Here we present a review on recent research on BP detectors operating from 0.26 THz to 3.4 THz with particular emphasis on the underlying physical mechanisms and the future challenges that are yet to be addressed for making BP the active core of stable and reliable optical and electronic technologies.

Optical and Optoelectronic Properties of Black Phosphorus and Recent Photonic and Optoelectronic Applications

“…Therefore, BP is expected to have a bright future in optoelectronic and photonic applications. [6,7,11,25,132] Photodetectors can convert information stored in light to electrical signals that can be processed by standard electronic equipment. Because of the direct bandgap and high carrier mobility, BP is promising in building broadband phototransistors for photodetection and imaging.…”

“…Few-layer BP films are capable of photodetection at terahertz (THz) frequencies by integrating with a microscopic FET. [25,[164][165][166][167][168] Because the THz photons do not carry enough energy to excite the bandgap optical transition in BP, signal conversion from optical to electrical must rely on either electronic or thermal effects (e.g., plasma-wave mixing, photo-thermoelectric, and bolometric effects). Viti et al have examined a THz photodetector based on a 10 nm thick BP flake as shown in Figure 11a.…”

“…The flexible bandgap modulation is expected to spur versatile photonic and optoelectronic applications of BP such as photodetectors and electro-optic modulators with broadband photoresponse spanning the visible and MIR regions. [11,[25][26][27] Another beneficial feature of BP is the relatively ideal tradeoff in the current on-off ratio for carrier mobility. Zhang and co-workers and Ye and co-workers have characterized the electrical transport properties of BP with a nanoscale thickness (≈10 nm).…”

Nanodevices at terahertz frequency based on 2D materials

“…Room temperature operation over the 1.8-4 THz range has been demonstrated with NEPs=80 pW Hz −1/2 , a dynamic range extending over four decades and a 40 ns response time [22]. THz photodetection has been also demonstrated in BP-based nano-detectors [21,30], exploiting the semiconductor-like behavior of BP. By exploiting the inherent electrical and thermal in-plane anisotropy of a flexible thin flake of BP, we have recently proved that we can engineer the detection dynamics from scratch, devising plasma-wave, thermoelectric or bolometric nano-detectors with a selective, switchable and controllable operating mechanism.…”

An Uwb Antenna Array for Flexible Iot Wireless Systems

“…The success of flexible electronics was greatly enabled by innovations in layered semiconductors and novel fabrication techniques [9][10][11][12][13][14][15][16]. Consequently, integrating flexible UWB and MIMO antennas with such devices is ultimately needed for advanced wireless connectivity.…”