| 1. |
- Amirmazlaghani, Mina, 1984, et al.
(författare)
-
Graphene-Si Schottky IR Detector
- 2013
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Ingår i: IEEE Journal of Quantum Electronics. - 0018-9197 .- 1558-1713. ; 49:7, s. 589-594
-
Tidskriftsartikel (refereegranskat)abstract
- This paper reports on photodetection properties of graphene-Si schottky junction by measuring current-voltage characteristics under 1.55µm excitation laser. The measurements have been done on a junction fabricated by depositing mechanically exfoliated natural graphite on top of the pre-patterned silicon substrate. The electrical Schottky barrier height is estimated to be (0.44-0.47) eV with a minimum responsivity of 2.8mA/W corresponding to an internal quantum efficiency of 10% which is almost an order of magnitude larger than regular Schottky junctions. A possible explanation for the large quantum efficiency related to the 2-D nature of graphene is discussed. Large quantum efficiency, room temperature IR detection, ease of fabrication along with compatibility with Si devices can open a doorway for novel graphene-based photodetectors.
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| 2. |
- ANDERSSON, MICHAEL, 1988, et al.
(författare)
-
10 dB small-signal graphene FET amplifier
- 2012
-
Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 48:14, s. 861-863
-
Tidskriftsartikel (refereegranskat)abstract
- Reported is the realisation of a graphene FET microwave amplifier operating at 1 GHz, exhibiting a small-signal power gain of 10 dB and a noise figure of 6.4 dB. The amplifier utilises a matching inductor on the gate yielding a return loss of 20 dB. The design is optimised for maximum gain and the optimum noise figure is extracted by noise modelling and predicted to be close to 1 dB for the intrinsic graphene FET at this frequency. The presented results complement existing graphene FET applications and are promising for future graphene microwave circuits.
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| 3. |
- ANDERSSON, MICHAEL, 1988, et al.
(författare)
-
Noise Figure Characterization of a Subharmonic Graphene FET Mixer
- 2012
-
Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781467310871
-
Konferensbidrag (refereegranskat)abstract
- We report on the first room temperature noise figure measurement of a graphene FET subharmonic resistive mixer in the interval fRF = 2-5 GHz. Due to an 8 nm thin Al2O3 gate dielectric it can operate with a conversion loss in the range 20-22 dB at only 0 dBm of local oscillator power. The measurement yields a noise figure close to the conversion loss, thus determining the noise to be thermal in origin, which is promising for cryogenic applications. The general route to lower noise figure is an improvement of the conversion loss.
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| 4. |
- ANDERSSON, MICHAEL, 1988, et al.
(författare)
-
Resistive Graphene FET Subharmonic Mixers: Noise and Linearity Assessment
- 2012
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:12, s. 4035-4042
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the first complete RF characterization of graphene field-effect transistor subharmonic resistive mixers in the frequency interval 2–5 GHz. The analysis includes conversion loss (CL), noise figure (NF), and intermodulation distortion. Due to an 8-nm thin Al2O3 gate dielectric, the devices operate at only 0 dBm of local oscillator (LO) power with an optimum measured CL in the range of 20–22 dB. The NF closely mimics the CL, thus determining the noise to be essentially thermal in origin, which is promising for cryogenic applications. The highest input third-order intercept point is measured to be 4.9 dBm at an LO power of 2 dBm.
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| 5. |
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| 6. |
- Engström, Olof, 1943, et al.
(författare)
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Properties of Metal/High-k Oxide/Graphene Structures
- 2017
-
Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 80:1, s. 157-176
-
Konferensbidrag (refereegranskat)abstract
- The challenge of interpreting experimental data from capacitance versus voltage (C-V) measurements on metal/high-k oxide/graphene (MOG) structures is discussed. Theoretical expressions for the influence of interface states, bulk oxide traps, measurement frequency, temperature and puddles are derived and compared with experiments. The nature of oxide traps and their impact on C-V data is treated especially from the view of electron-lattice interaction at electron emission and capture and possible performance as border traps, resembling interface states. We find that characterization on detailed physical origins leading to effects on C-V data is a more complicated issue than the corresponding analysis of metal/oxide/semiconductor (MOS) structures.
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| 7. |
- Guerriero, E., et al.
(författare)
-
High-Gain Graphene Transistors with a Thin AlOx Top-Gate Oxide
- 2017
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 7:1
-
Tidskriftsartikel (refereegranskat)abstract
- The high-frequency performance of transistors is usually assessed by speed and gain figures of merit, such as the maximum oscillation frequency f(max), cutoff frequency f(T), ratio f(max)/f(T), forward transmission coefficient S-21, and open-circuit voltage gain A(v). All these figures of merit must be as large as possible for transistors to be useful in practical electronics applications. Here we demonstrate high-performance graphene field-effect transistors (GFETs) with a thin AlOx gate dielectric which outperform previous state-of-the-art GFETs: we obtained f(max)/f(T) > 3, A(v) > 30 dB, and S-21 = 12.5 dB (at 10 MHz and depending on the transistor geometry) from S-parameter measurements. A dc characterization of GFETs in ambient conditions reveals good current saturation and relatively large transconductance similar to 600 S/m. The realized GFETs offer the prospect of using graphene in a much wider range of electronic applications which require substantial gain.
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| 8. |
- Habibpour, Omid, 1979, et al.
(författare)
-
A 30-GHz Integrated Subharmonic Mixer based on a Multichannel Graphene FET
- 2013
-
Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 61:2, s. 841-847
-
Tidskriftsartikel (refereegranskat)abstract
- A 30 GHz integrated subharmonic mixer based on a single graphene field effect transistor (G-FET) has been designed, fabricated and characterized. The mixer is realized in microstrip technology on a 250 um high resistivity silicon substrate. In order to enhance the current on-off ratio, the G-FET utilizes a channel consisting of an array of bow-tie structured graphene, yielding a current on-off ratio of 7. A conversion loss (CL) of 19 ± 1 dB over the frequency range of 24 to 31 GHz is obtained with an LO to RF isolation better than 20 dB at an LO power of 10 dBm. The overall minimum CL is 18 dB at 27 GHz. The mixer has a 3 GHz ±1-dB IF bandwidth, which is achieved with a fixed LO signal of 15 GHz. The mixer linearity is characterized and the highest third order intercept point is measured to be 12.8 dBm.
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| 9. |
- Habibpour, Omid, 1979, et al.
(författare)
-
A Large Signal Graphene FET Model
- 2012
-
Ingår i: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 59:4, s. 968-975
-
Tidskriftsartikel (refereegranskat)abstract
- We propose a semiempirical graphene field effect transistor (G-FET) model for analysis and design of G-FET based circuits. The model describes the current-voltage characteristic for a G-FET over a wide range of operating conditions. The gate bias dependence of the output power spectrum is studied and compared with simulated values. A good agreement between the simulated and the experimental power spectrum up to the 3rd harmonic is demonstrated which confirms the model validity. Moreover, S-parameter measurements essentially coincide with the results obtained from the simulation. The model contains a small set of fitting parameters which can straightforwardly be extracted from S-parameters and DC measurements. The developed extraction method gives a more accurate estimation of the drain and source contact resistances compared to other approaches. As a design example, we use a harmonic-balance load-pull approach to extract optimum embedding impedances for a subharmonic G-FET mixer.
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| 10. |
- Habibpour, Omid, 1979, et al.
(författare)
-
A subharmonic graphene FET mixer
- 2012
-
Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 33:1, s. 71-73
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a subharmonic resistive graphene FET (G-FET) mixer utilizing the symmetrical channel resistance vs. gate voltage characteristic. A down-conversion loss of 24 dB is obtained with fRF=2 GHz, fLO=1.01 GHz and fIF=20 MHz in a 50 Ω impedance system. Unlike the conventional subharmonic resistive FET mixers, this type of mixer operates with only one transistor and does not need any balun at the LO port which makes it more compact.
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| 11. |
- Habibpour, Omid, 1979, et al.
(författare)
-
A W-band MMIC Resistive Mixer Based on Epitaxial Graphene FET
- 2017
-
Ingår i: IEEE Microwave and Wireless Components Letters. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-1764 .- 1531-1309. ; 27:2, s. 168-170
-
Tidskriftsartikel (refereegranskat)abstract
- This letter presents the design, fabrication and characterization of the first graphene based monolithic microwave integrated circuit (MMIC) in microstrip technology operating in W-band. The circuit is a resistive mixer in a 250 nm graphene field effect transistor (G-FET) technology on a SiC substrate. A conversion loss of 18 dB is achieved which is limited by the available local oscillator (LO) power. The mixer exhibits a flat response over radio frequency (RF) range of 90-100 GHz. The RF bandwidth is also limited by the measurement setup.
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| 12. |
- Habibpour, Omid, 1979, et al.
(författare)
-
Characterisation of Exfoliated Graphene
- 2009
-
Ingår i: WOCSDICE 2009.
-
Konferensbidrag (refereegranskat)abstract
- High-frequency devices based on graphene is a promising field of research. In this paper we investigate two important parameters which based on theory are essential in order to have nonlinear responses in graphene. The first parameter is scattering time which should be as high as 1ps. Also the electrical field of the incident radiation should be higher a certain threshold in order to have nonlinear response. This threshold is generally quite high and increases with frequency and carrier density, so it is essential that graphene flake tolerate high electrical field. The first condition cannot be reached by graphene on SiO2/Si substrate according to ourinvestigation.
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| 13. |
- Habibpour, Omid, 1979, et al.
(författare)
-
Developing Graphene based MMICs on SiC substrate
- 2016
-
Ingår i: 2015 Asia-Pacific Microwave Conference (Apmc), Vols 1-3. ; 1
-
Konferensbidrag (refereegranskat)abstract
- This paper presents the fabrication process development of monolithic microwave integrated circuits (MMICs) based on graphene field effect transistors (G-FETs). In this process, the G-FETs are based on epitaxial graphene on SiC substrate. Base on this process, a wide-band amplifier (0-3GHz) with 6-7 dB gain is realized.
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| 14. |
- Habibpour, Omid, 1979
(författare)
-
Fabrication, Characterisation and Modelling of Subharmonic Graphene FET Mixers
- 2011
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Graphene has exceptional carrier transport properties which makes it a promising material for future nanoelectronics. The high carrier mobility along with the ability to switch between n- and p-channel in a graphene field effect transistor (G-FET) truly distinguishes it from other types of FET technologies and enables completely new high frequency devices.In this thesis, a novel subharmonic resistive G-FET mixer is presented. The mixer operation is based on the G-FET’s symmetrical transfer characteristic. Due to this property, the mixer operates with a single transistor and unlike the conventional subharmonic resistive FET mixers, it does not need any balun at the local oscillator (LO) port. This makes the mixer circuit more compact. The mixer conversionloss (CL) is measured with fRF=2 GHz, fLO=1.01 GHz and fIF=20 MHz in a 50 Ω impedance system, and for a G-FET with an on-off ratio of 3, a CL of 24 dB is obtained. In addition, the mixer performance is analysed based on the GFET parameters, the LO power and the embedding impedances. It is predicted that by having a G-FET with an on-off ratio of 10 and selecting proper embedding impedances, a CL of 17 dB is attainable. Also, by further improvement of theG-FET on-off ratio, the CL is optimised to about 14.2 dB.Moreover, a process technology for 1 μm gate-length G-FETs based on exfoliated graphene has been developed. A contact resistance as low as 500-600 Ω.μm is obtained, which is close to the lowest reported value. In addition, different gate dielectric materials have been investigated. A plasma enhanced chemical vapour deposition (PECVD) process for deposition of a silicon nitride film as a gate dielectricis developed. The process maintains the carrier mobility of the graphene film largely intact after deposition. Also, to form Al2O3 gate dielectric films, a protective layer of naturally oxidised Al is used prior to e-gun evaporation of Al2O3. This layer prevents further degradation of the carrier mobility. Finally, a novel closed-form large-signal model for G-FETs is developed. The model is semiempirical and can be utilised in standard Electronic Design Automation (EDA) tools for designing and analysing G-FET circuits. The model is implemented in Agilent’s Advanced Design System (ADS) software and experimentally verified for a G-FET under both DC and RF operation. The DC results agree with the model. The RF verification includes S-parameters and power spectrum measurements. The S-parameters measurements essentially coincide with the model and the power spectrum analysis shows good agreement up to the 4th order. Moreover, the model is used to simulate the G-FET mixer CL and the results follow the measurements.
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| 15. |
- Habibpour, Omid, 1979, et al.
(författare)
-
Generation of multi-Gigabit/s OFDM signals at W-band with a graphene FET MMIC mixer
- 2017
-
Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781509063604 ; , s. 1185-1187
-
Konferensbidrag (refereegranskat)abstract
- This paper presents multi-Gigabit/s Orthogonal Frequency Division Multiplexing (OFDM) signal generation by using a graphene field effect transistor based resistive mixer at w-band. The OFDM signals consist of 64 subcarriers each carrying a quadrature-phase-shift-keying (QPSK) symbols. The results show that a bit error rate of 10 -4 is achievable for 8 Gbps data rate.
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| 16. |
- Habibpour, Omid, 1979, et al.
(författare)
-
Generic Graphene Based Components and Circuits for Millimeter Wave High Data-rate Communication Systems
- 2017
-
Ingår i: MRS Advances. - : Springer Science and Business Media LLC. - 2059-8521. ; 2:58-59, s. 3559-3564
-
Tidskriftsartikel (refereegranskat)abstract
- We are developing millimeter wave (mm-wave) components and circuits based on hydrogen-intercalated graphene. The development covers epitaxial graphene growth, device fabrication, modelling, integrated circuit design and fabrication, and circuit characterizations. The focus of our work is to utilize the distinctive graphene properties and realize new components that can overcome some of the main challenges of existing mm-wave technologies in term of linearity.
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| 17. |
- Habibpour, Omid, 1979, et al.
(författare)
-
Graphene FET Gigabit On-Off Keying Demodulator at 96 GHz
- 2016
-
Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 37:3, s. 333-336
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the demodulation of a multi-Gb/s ON-OFF keying (OOK) signal on a 96 GHz carrier by utilizing a 250-nm graphene field-effect transistor as a zero bias power detector. From the eye diagram, we can conclude that the devices can demodulate the OOK signals up to 4 Gb/s.
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| 18. |
- Habibpour, Omid, 1979
(författare)
-
Graphene FETs in Microwave Applications
- 2012
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Graphene is a one-atom-thick sheet of carbon with numerous impressive properties. It is a promising material for future high-speed nanoelectronics due to its intrinsic superior carrier mobility and very high saturation velocity. These exceptional carrier transport properties suggest that graphene field effect transistors (G-FETs) canpotentially outperform other FET technologies. This doctoral thesis presents the realisation of G-FET circuits at microwave frequencies (0.3-30 GHz) with emphasis on a novel subharmonic resistive mixer. The work covers device manufacturing, modelling, circuit design, and characterisation. The developed mixer exploits the G-FETs ability to conduct current in both n-channel and p-channel modes for subharmonic (×2) mixing. Consequently, the mixer operates with a single transistor and unlike the conventional subharmonic resistive FET mixers, it does not need any balun at the local oscillator (LO) port. In addition, the mixer has potential to operate unbiased. These aspects enable us to utilise G-FET subharmonic mixers in compact high frequency heterodyne detectors.A 30 GHz mixer is realised in microstrip technology on a 250 μm high resistivity silicon substrate. A conversion loss (CL) of 19 ± 1 dB in the frequency range of 24 to 31 GHz is obtained with an LO to RF isolation better than 20 dB. For designing and analysing G-FET circuits a closed-form semiempirical largesignal model is proposed and experimentally verified under both DC and RF operation.The model is implemented in a standard Electronic Design Automation (EDA) software for device-circuit co-design. By using the model, the first G-FET microwave amplifier is realised. The amplifier exhibits a small-signal power gain of 10 dB at 1 GHz.
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| 19. |
- Habibpour, Omid, 1979, et al.
(författare)
-
High gain graphene field effect transistors for wideband amplifiers
- 2014
-
Ingår i: 44th European Microwave Conference, EuMC 2014 - Held as Part of the 17th European Microwave Week, EuMW 2014; Fiera di RomaRome; Italy; 6 October 2014 through 9 October 2014. - 9782874870354 ; , s. 371-373
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate graphene field of transistors (G-FETs) providing power gain of > 7 dB in a 50 O system. The G-FETs have S21 > 0 dB up to 7 GHz. The result indicates the feasibility for G-FET based wideband amplifiers.
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| 20. |
|
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| 21. |
- Habibpour, Omid, 1979, et al.
(författare)
-
Mobility Improvement and Microwave Characterization of a Graphene Field Effect Transistor With Silicon Nitride Gate Dielectrics
- 2011
-
Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 32:7, s. 871-873
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the influence of a silicon nitride gate dielectric in graphene-based field-effect transistors (FETs). The silicon nitride is formed by a plasma enhanced chemical vapor deposition method. The process is based on a low density plasma at a high pressure (1 torr), which results in a low degradation of the graphene lattice during the top-gate formation process. Microwave measurements of the graphene FET show a cutoff frequency of 8.8 GHz for a gate length of 1.3 μm. A carrier mobility of 3800 cm2/V · s at room temperature was extracted from the dc characteristic.
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| 22. |
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| 23. |
- Habibpour, Omid, 1979, et al.
(författare)
-
Wafer scale millimeter-wave integrated circuits based on epitaxial graphene in high data rate communication
- 2017
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 7, s. 41828-
-
Tidskriftsartikel (refereegranskat)abstract
- In recent years, the demand for high data rate wireless communications has increased dramatically, which requires larger bandwidth to sustain multi-user accessibility and quality of services. This can be achieved at millimeter wave frequencies. Graphene is a promising material for the development of millimeter-wave electronics because of its outstanding electron transport properties. Up to now, due to the lack of high quality material and process technology, the operating frequency of demonstrated circuits has been far below the potential of graphene. Here, we present monolithic integrated circuits based on epitaxial graphene operating at unprecedented high frequencies (80-100 GHz). The demonstrated circuits are capable of encoding/decoding of multi-gigabit-per-second information into/from the amplitude or phase of the carrier signal. The developed fabrication process is scalable to large wafer sizes.
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| 24. |
- Hamed, Ahmed, et al.
(författare)
-
W-Band Graphene-Based Six-Port Receiver
- 2018
-
Ingår i: IEEE Microwave and Wireless Components Letters. - 1558-1764 .- 1531-1309. ; 28:4, s. 347-349
-
Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a full-fledged millimeter-wave graphene-based six-port receiver frontend at 90 GHz employing graphene power detectors. Exploiting the high responsivity and wide dynamic range reported for the state-of-the-art graphene field-effect transistors (GFETs), graphene power detectors are demonstrated beyond the maximum oscillation frequency, f max , of the graphene transistor. The proposed circuit is fabricated on thinned SiC substrate and its functionality is verified by demodulation of 10-Mbps ON-OFF keying (OOK) digitally modulated signal.
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| 25. |
- Hassona, Ahmed Adel, 1988, et al.
(författare)
-
A Low-loss D-band Chip-to-Waveguide Transition Using Unilateral Fin-line Structure
- 2018
-
Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. ; 2018-June, s. 390-393
-
Konferensbidrag (refereegranskat)abstract
- This paper presents a D-band interconnect realized using unilateral finline structure. The interconnect consists of a microstrip line implemented on a 75μm-thick SiC substrate. The line then couples to a unilateral finline taper that is mounted in the E-plane of a standard WR-6.5 D-band waveguide. The interconnect achieves low insertion loss and covers very wide frequency range. The measured minimum insertion loss is 0.67 dB and the maximum is 2 dB per transition across the entire D-band covering the frequency range 110-170 GHz. The transition does not require any galvanic contacts nor any special processing and can be implemented in any of the commercially available semiconductor technologies. This solution provides low-loss wideband packaging technique that enables millimeter-wave systems assembly using a high-performance simple approach.
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| 26. |
- Hassona, Ahmed Adel, 1988, et al.
(författare)
-
Nongalvanic Generic Packaging Solution Demonstrated in a Fully Integrated D-Band Receiver
- 2020
-
Ingår i: IEEE Transactions on Terahertz Science and Technology. - 2156-342X .- 2156-3446. ; 10:3, s. 321-330
-
Tidskriftsartikel (refereegranskat)abstract
- This article presents a packaging technique for monolithic microwave integrated circuits (MMIC) demonstrated in a fully integrated receiver (Rx) module at the D -band (110–170 GHz). The solution consists of an MMIC-to-waveguide transition realized using an on-chip probe mounted in the E -plane of a split-block waveguide module. An artificial magnetic conductor structure is implemented to suppress cavity modes and achieve better coupling from the waveguide to the probe. The transition's performance is experimentally verified using a back-to-back test chip, and measurement results show that the proposed packaging solution achieves a low insertion loss of only 0.7 dB and covers a very wide frequency range extending from 105 to 175 GHz. The proposed transition is also integrated with an in-phase/quadrature-phase (I/Q) Rx on the same chip. The Rx is realized in a 250-nm indium phosphide double heterojunction bipolar transistor technology and consists of a low-noise amplifier, an I/Q mixer, and a frequency tripler. Measurement results show that the Rx module achieves an average conversion gain of 23 dB across the frequency range of 110–145 GHz and has an average noise figure of 10.6 dB. The Rx MMIC has a dc power consumption of 440 mW and occupies an area of 1.6 × 1.6 mm 2 . This article addresses one of the main challenges in systems operating above 100 GHz and presents a fully integrated packaging solution that suits large integrated circuits and does not require any galvanic contacts nor impose any limitations on MMIC dimensions.
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| 27. |
- Ribero-Figueroa, Xiomara, et al.
(författare)
-
Characterization of the Intrinsic and Extrinsic Resistances of a Microwave Graphene FET Under Zero Transconductance Conditions
- 2023
-
Ingår i: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 70:11, s. 5977-5982
-
Tidskriftsartikel (refereegranskat)abstract
- Graphene field-effect transistors (GFETs) exhibit negligible transconductance under two scenarios: for any gate-to-source voltage when the drain-to-source voltage is set to zero and for an arbitrary drain-to-source voltage provided that the gate-to-source voltage equals the Dirac voltage. Hence, extracting the channel and the parasitic series resistances from S-parameters under these conditions enables analyzing their dependence on the gate and drain biases. This is fundamental to assess the portion of the output resistance that is controlled by the gate. Besides, the drain bias dependence of the drain and source resistances is also evidenced. Within the proposal, resistive components accounting for the lossy nature of the gate capacitance are incorporated into the model, which exhibits a broadband correlation with experimental data. This avoids the series resistances to be considered as frequency dependent in the model.
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| 28. |
- Stake, Jan, 1971, et al.
(författare)
-
Graphene Millimeter Wave Electronics
- 2011
-
Ingår i: 6th ESA Workshop on Millimetre-Wave Technology and Applications and 4th Global Symposium on Millimeter Waves.
-
Konferensbidrag (refereegranskat)abstract
- We report on the development of graphene based transistors and circuits for millimeter wave applications.
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| 29. |
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| 30. |
- Stake, Jan, 1971, et al.
(författare)
-
The rise of graphene in microwave and THz applications
- 2013
-
Ingår i: The Swedish-Japan workshop on quantum nano-physics and electronics. ; , s. 27-
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Graphene, a single layer of carbon atoms, has extremely high intrinsic carrier mobility and high carrier saturation velocity, which identifies it as a potential material for high-frequency and terahertz electronics. Applications in the THz range have traditionally been limited radio astronomy. On the other hand, ground-based applications in high-speed data communications, spectroscopy and imaging are emerging. For these applications, having silicon compatible technology is a great advantage since it allows the integration of RF and digital circuits as well as antennas/waveguides on a single chip. Since graphene is compatible with silicon, and thanks to unique transport properties, this 2D material system opens up for a complete new platform for advanced THz sensor systems. In this talk, we will present the current status of graphene devices and circuits for microwave applications, including mixers [1-2] operating up to 30 GHz [3] and microwave amplifiers [4].
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| 31. |
- ul-Hassan, Jawad, et al.
(författare)
-
Quasi-free-standing monolayer and bilayer graphene growth on homoepitaxial on-axis 4H-SiC(0001) layers
- 2015
-
Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 82:C, s. 12-23
-
Tidskriftsartikel (refereegranskat)abstract
- Quasi-free-standing monolayer and bilayer graphene is grown on homoepitaxial layers of 4H-SiC. The SiC epilayers themselves are grown on the Si-face of nominally on-axis semi-insulating substrates using a conventional SiC hot-wall chemical vapor deposition reactor. The epilayers were confirmed to consist entirely of the 4H polytype by low temperature photoluminescence. The doping of the SiC epilayers may be modified allowing for graphene to be grown on a conducing substrate. Graphene growth was performed via thermal decomposition of the surface of the SiC epilayers under Si background pressure in order to achieve control on thickness uniformity over large area. Monolayer and bilayer samples were prepared through the conversion of a carbon buffer layer and monolayer graphene respectively using hydrogen intercalation process. Micro-Raman and reflectance mappings confirmed predominantly quasi-free-standing monolayer and bilayer graphene on samples grown under optimized growth conditions. Measurements of the Hall properties of Van der Pauw structures fabricated on these layers show high charge carrier mobility (> 2000 cm(2)/Vs) and low carrier density (
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| 32. |
- Vukusic, Josip, 1972, et al.
(författare)
-
Heterogeneous integration of terahertz electronics
- 2015
-
Ingår i: Global symposium on millimeter-waves (GSMM) 2015.
-
Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Abstract: Compact heterodyne receivers operating in the terahertz range are needed for earth observation instruments, space science missions (e.g. ESA’s “Jupiter icy moons explorer - JUICE”) and in the millimeter wave region for ground-based applications such as security scanners. Existing terahertz heterodyne receivers are usually bulky due to complex hybrid integration and there is a strong need for a terahertz monolithic integration circuit (“TMIC”) platform that allows for higher circuit functionality, ease of assembly, and low loss at terahertz frequencies. Moreover, this part of the electromagnetic spectrum, where optical and microwave techniques meet, call for an integration scheme that can support both active THz electronics & photonics. A possible solution is heterogeneous integration of THz devices (III-V, graphene) on a silicon carrier, which also allows for advanced micromaching of passive components and interconnects such as waveguides and antennas. This talk provides an overview of research on integrated diode circuits for terahertz applications. Progress on heterogeneous integration of HBV multipliers and Schottky diode mixers on silicon substrates (SOI) will be presented.
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| 33. |
- Winters, Michael, 1986, et al.
(författare)
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Assessment of H-intercalated graphene for microwave FETs through material characterization and electron transport studies
- 2015
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Ingår i: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 81:1, s. 96-104
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Tidskriftsartikel (refereegranskat)abstract
- Epitaxial graphene is grown on semi-insulating (SI) 4H-SiC in a hot wall CVD reactor by graphitization and in-situ intercalation with (H)ydrogen. A holistic material characterization is performed in order to ascertain the number of layers, layer uniformity, and electron transport properties of the epi-layers via electronic test structures and Raman spectroscopy. Bilayer graphene field effect transistors (GFETs) are fabricated using a full electron beam lithography (EBL) process which is optimized for low contact resistances of r(c)
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