Low Carrier Density Epitaxial Graphene Devices On SiC

Yang, Yue; Huang, Lung-I; Fukuyama, Yasuhiro; Liu, Fan-Hung; Real, Mariano; Barbara, Paola; Liang, Chi‐Te; Newell, David B.; Elmquist, Randolph E.

doi:10.1002/smll.201400989

Cited by 63 publications

(69 citation statements)

References 31 publications

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“…This non-uniform doping could be either introduced during the graphene growth or caused by the photochemical gating. If the latter is the case, the problem can possibly be avoided by using other methods of controlling the carrier density, such us doping by exposure to different environments 18,28,29 or gating by corona discharge 30 .…”

Section: Measurements Of the Quantum Hall Resistancementioning

confidence: 99%

A prototype of RK/200 quantum Hall array resistance standard on epitaxial graphene

Lartsev

Lara‐Avila

Danilov

et al. 2015

Journal of Applied Physics

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Epitaxial graphene on silicon carbide is a promising material for the next generation of quantum Hall resistance standards. Single Hall bars made of graphene have already surpassed their state-of-the-art GaAs based counterparts as an R K /2 (R K = h/e 2 ) standard, showing at least the same precision and higher breakdown current density. Compared to single devices, quantum Hall arrays using parallel or series connection of multiple Hall bars can offer resistance values spanning several orders of magnitude and (in case of parallel connection) significantly larger measurement currents, but impose strict requirements on uniformity of the material. To evaluate the quality of the available material, we have fabricated arrays of 100 Hall bars connected in parallel on epitaxial graphene. One out of four devices has shown quantized resistance that matched the correct value of R K /200 within the measurement precision of 10 −4 at magnetic fields between 7 and 9 Tesla. The defective behaviour of other arrays is attributed mainly to non-uniform doping. This result confirms the acceptable quality of epitaxial graphene, pointing towards the feasibility of well above 90% yield of working Hall bars.

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Section: Measurements Of the Quantum Hall Resistancementioning

confidence: 99%

A prototype of RK/200 quantum Hall array resistance standard on epitaxial graphene

Lartsev

Lara‐Avila

Danilov

et al. 2015

Journal of Applied Physics

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“…We fabricated our dots using e-beam lithography and a process developed by Yang et al, 8 (see Methods). One important characteristic of bolometric sensors is the noise equivalent power (NEP), which is the lowest detectable power in a 1Hz output bandwidth.…”

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confidence: 99%

Epitaxial graphene quantum dots for high-performance terahertz bolometers

et al. 2016

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2Light absorption in graphene causes a large change in electron temperature, due to low electronic heat capacity and weak electron phonon coupling, 1-3 making it very attractive as a hot-electron bolometer material. Unfortunately, the weak variation of electrical resistance with temperature has substantially limited the responsivity of graphene bolometers. Here we show that quantum dots of epitaxial graphene on SiC exhibit an extraordinarily high variation of resistance with temperature due to quantum confinement, higher than 430 M K -1 at 2.5 K, leading to responsivities for absorbed THz power above 1 × 10 10 V W -1 . This is five orders of magnitude higher than other types of graphene hot electron bolometers. The high responsivity combined with an extremely low noise-equivalent power, about 2 × 10 -16 W/√Hz at 2.5K, place the performance of graphene quantum dot bolometers well above commercial cooled bolometers. Additionally, these quantum dot bolometers have the potential for superior performance for operation above 77K.The electrical resistivity of pristine graphene shows a weak temperature dependence, varying by less than 30% (200% for suspended graphene) from 30 mK to room temperature 4,5 , because of the very weak electron-phonon scattering 6 . A stronger temperature dependence was obtained either by using dual-gated bilayer graphene 1,7 to create a tunable band gap 7 , or by introducing defects to induce strong localization 2 . Both schemes have successfully produced bolometric detection, with responsivities up to 2 × 10 5 V W -1 and temperature coefficient for the resistance as high as 22 kK -1 at 1.5K 1,2 . These devices required the use of multilayer structures adding complexity. In the case of bilayer graphene, top and bottom gates were needed to electrically induce a bandgap. In the case of disordered graphene, a boron nitride layer was used as a tunneling barrier between the graphene and the electrodes to reduce thermal conductance due to diffusion of the electrons to the electrodes. 3Here we demonstrate hot-electron bolometric detection using nano-patterned dots of epitaxial graphene. A bandgap is induced via quantum confinement, without the need of gates, using a simple single-layer structure. We study the THz response of dots with diameter varying from 30 nm to 700 nm, at 0.15 THz and at temperatures from 2.5K to 80K. These devices are extremely sensitive and the responsivity increases by decreasing the dot diameter, with the smaller dots still showing a clear response at liquid nitrogen temperature. Our fabrication process is fully scalable and easily provides multiple devices on the same chip, making it suitable for bolometer arrays. Moreover, its flexibility allows patterning of arrays of dots electrically connected in parallel, to control the device impedance while preserving the strong temperature dependence.We fabricated our dots using e-beam lithography and a process developed by Yang et al., 8 (see Methods). Fig. 1a shows an image of a typical quantum dot and the temperature dependenc...

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“…The wafers were diced to obtain specimen size of 7.8 mm × 3.7 mm. The substrates were then annealed at 1900°C in Argon at (101–105) kPa using a controlled Si sublimation process, which stops at one mono-layer on Si-terminated face [10]. After removing the graphene material on the C-terminated face [10], several SiC/G samples were tested directly in the microwave cavity on the native substrate.…”

Section: Experimentalb)mentioning

confidence: 99%

“…The specimen is suspended inside the cavity without contacting the cavity walls, which simplifies the cavity perturbation problem and minimizes the effect of charge carrier heating from parasitic current loops. We compare these non-contact results with the DC longitudinal Hall resistance measurements of epitaxial mono-layer graphene grown on silicon carbide [6,10]. …”

Section: Introductionmentioning

confidence: 99%

Surface conductance of graphene from non-contact resonant cavity

et al. 2016

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A method is established to reliably determine surface conductance of single-layer or multi-layer atomically thin nano-carbon graphene structures. The measurements are made in an air filled standard R100 rectangular waveguide configuration at one of the resonant frequency modes, typically at TE103 mode of 7.4543 GHz. Surface conductance measurement involves monitoring a change in the quality factor of the cavity as the specimen is progressively inserted into the cavity in quantitative correlation with the specimen surface area. The specimen consists of a nano-carbon-layer supported on a low loss dielectric substrate. The thickness of the conducting nano-carbon layer does not need to be explicitly known, but it is assumed that the lateral dimension is uniform over the specimen area. The non-contact surface conductance measurements are illustrated for a typical graphene grown by chemical vapor deposition process, and for a high quality monolayer epitaxial graphene grown on silicon carbide wafers for which we performed non-gated quantum Hall resistance measurements. The sequence of quantized transverse Hall resistance at the Landau filling factors ν = ±6 and ±2, and the absence of the Hall plateau at ν = 4 indicate that the epitaxially grown graphene is a high quality mono-layer. The resonant microwave cavity measurement is sensitive to the surface and bulk conductivity, and since no additional processing is required, it preserves the integrity of the conductive graphene layer. It allows characterization with high speed, precision and efficiency, compared to transport measurements where sample contacts must be defined and applied in multiple processing steps.

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Low Carrier Density Epitaxial Graphene Devices On SiC

Cited by 63 publications

References 31 publications

A prototype of RK/200 quantum Hall array resistance standard on epitaxial graphene

A prototype of RK/200 quantum Hall array resistance standard on epitaxial graphene

Epitaxial graphene quantum dots for high-performance terahertz bolometers

Surface conductance of graphene from non-contact resonant cavity

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