Abstract
AbstractUltrafast and sensitive (noise equivalent power <1 nW Hz−1/2) light-detection in the terahertz (THz) frequency range (0.1–10 THz) and at room-temperature is key for applications such as time-resolved THz spectroscopy of gases, complex molecules and cold samples, imaging, metrology, ultra-high-speed data communications, coherent control of quantum systems, quantum optics and for capturing snapshots of ultrafast dynamics, in materials and devices, at the nanoscale. Here, we report room-temperature THz nano-receivers exploiting antenna-coupled graphene field effect transistors integrated with lithographically-patterned high-bandwidth (∼100 GHz) chips, operating with a combination of high speed (hundreds ps response time) and high sensitivity (noise equivalent power ≤120 pW Hz−1/2) at 3.4 THz. Remarkably, this is achieved with various antenna and transistor architectures (single-gate, dual-gate), whose operation frequency can be extended over the whole 0.1–10 THz range, thus paving the way for the design of ultrafast graphene arrays in the far infrared, opening concrete perspective for targeting the aforementioned applications.
Highlights
Hot-carrier assisted photodetection is an efficient and inherently broadband detection mechanism in single layer graphene (SLG) [1,2,3,4]
By embedding the hBN/SLG/hBN layered materials heterostructures (LMH) [29, 30] in FET coupled to on-chip planar THz antennas (Figure 1A and B), we demonstrate ultrafast (τ < 1 ns) detection of >3 THz light at room temperature (RT), with a record combination of speed, NEP and sensitivity, independent on the specific architecture
The thickness of hBN is determined by atomic force microscope (AFM) and Raman spectroscopy [37, 38]
Summary
Hot-carrier assisted photodetection is an efficient and inherently broadband detection mechanism in single layer graphene (SLG) [1,2,3,4]. The electron-to-lattice relaxation via acoustic phonons is slower (1–2 ps) [6], leading to a quasiequilibrium state where the thermal energy is distributed amongst electrons [5, 6] and not shared with the lattice. This produces an intriguing scenario, where the energy is absorbed by a system with an extremely low thermal capacitance (ce ∼ 2000 kBμm−2, kB is the Boltzmann constant) [7,8,9,10], leading to the ultrafast (∼fs−ps) onset of thermal gradients in SLG-based nanostructures. SLG is a promising material for engineering high-speed (∼ps response time) optoelectronic THz devices that could benefit from the above mechanism [12]
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