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).

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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.