Abstract-Nanostructured epitaxial graphene for ultra-broadband optoelectronic detectors (Conference Presentation)

Abdel El Fatimy,  Luke St. Marie,  Anindya Nath, Byoung Don Kong, Anthony K. Boyd,  Rachael L. Myers-Ward,  Kevin M. Daniels,  M. Mehdi Jadidi,  Thomas E. Murphy,  D. Kurt Gaskill, Paola Barbara

https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10729/1072906/Nanostructured-epitaxial-graphene-for-ultra-broadband-optoelectronic-detectors-Conference-Presentation/10.1117/12.2321313.short

Atomically thin materials like semimetallic graphene and semiconducting transition metal dichalcogenides (TMDs) are an ideal platform for ultra-thin optoelectronic devices due to their direct bandgap (for monolayer thickness) and their considerable light absorption. For devices based on semiconducting TMDs, light detection occurs by optical excitation of charge carriers above the bandgap. For gapless graphene, light absorption causes a large increase in electron temperature, because of its small electronic heat capacity and weak electron-phonon coupling, making it suitable for hot-electron detectors. Here we show that, by nanostructuring graphene into quantum dots, we can exploit quantum confinement to achieve hot-electron bolometric detection. The graphene quantum dots are patterned from epitaxial graphene on SiC, with dot diameter ranging from 30 nm to 700 nm [1]. Nanostructuring greatly increases the temperature dependence of the electrical resistance, yielding detectors with extraordinary performance (responsivities of 1 × 10^(10) V W^(−1) and electrical noise-equivalent power, ∼2 × 10^(−16) W Hz^(−1/2) at 2.5 K). We will discuss how the dynamics of the charge carriers, namely the hot-electron cooling, affects the device operation and its power dependence. These detectors work in a very broad spectral range, from terahertz through telecom to ultraviolet radiation [2], with a design that is easily scalable for detector arrays. [1] El Fatimy, A. et al. , "Epitaxial graphene quantum dots for high-performance terahertz bolometers," Nature Nanotechnology 11, 335-338 (2016). [2] El Fatimy, A. et al. , "Ultra-broadband photodetectors based on epitaxial graphene quantum dots" Nanophotonics (2018).

© (2018) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

Abstract-Epitaxial graphene quantum dots for high-performance terahertz bolometer

• Abdel El Fatimy,
• Rachael L. Myers-Ward,
• Anthony K. Boyd,
• Kevin M. Daniels,
• D. Kurt Gaskill
• & Paola Barbara,

http://www.nature.com/nnano/journal/vaop/ncurrent/full/nnano.2015.303.html

Light absorption in graphene causes a large change in electron temperature due to the low electronic heat capacity and weak electron–phonon coupling^1, 2, 3. This property makes graphene a very attractive material for hot-electron bolometers in the terahertz frequency range. Unfortunately, the weak variation of electrical resistance with temperature results in limited responsivity for absorbed power. Here, we show that, due to quantum confinement, quantum dots of epitaxial graphene on SiC exhibit an extraordinarily high variation of resistance with temperature (higher than 430 MΩ K⁻¹below 6 K), leading to responsivities of 1 × 10¹⁰ V W⁻¹, a figure that is five orders of magnitude higher than other types of graphene hot-electron bolometer. The high responsivity, combined with an extremely low electrical noise-equivalent power (∼2 × 10⁻¹⁶ W Hz^−1/2 at 2.5 K), already places our bolometers well above commercial cooled bolometers. Additionally, we show that these quantum dot bolometers demonstrate good performance at temperature as high as 77 K.

Abstract-Hybrid Metal-Graphene Plasmons for Tunable Terahertz Optoelectronics

Mohammad M. Jadidi, Andrei B. Sushkov, Rachael L. Myers-Ward, Anthony K. Boyd, Kevin M. Daniels, D.Kurt Gaskill, Michael S. Fuhrer, H.Dennis Drew, Thomas E. Murphy

(Submitted on 18 Jun 2015)

http://xxx.tau.ac.il/abs/1506.05817

Graphene has unique and advantageous electronic and optical properties, especially in the underdeveloped terahertz range of the electromagnetic spectrum. Sub-micron graphene structures support terahertz (THz) plasmonic resonances that can be tuned by applying a gate voltage. Because these plasmonic structures are sub-wavelength in size, they need to be integrated with a THz antenna or a metamaterial structure to optimize the graphene coupling to the free space radiation. Furthermore, nearly all THz optoelectronic applications including detectors, filters, and modulators require electrical connection or antenna coupling to the graphene, which inhibits the accumulation of charge at the edges of the graphene. Here, we present the first observation and systematic study of plasmon resonances in a hybrid graphene-metal design in which the graphene acts as a gate-tuneable inductor, and metal as a capacitive reservoir for charge accumulation. We experimentally demonstrate a large resonant absorption in low-mobility graphene (μ=1000 cm2V−1s−1), and show that the peak can approach 100% in an optimized device, ideal for graphene-based THz detectors. We predict that use of high mobility graphene (μ>50000 cm2V−1s−1) will allow resonant THz transmission near 100%, realizing a near perfect tunable THz filter or modulator.