| 1. |
- Amirmazlaghani, Mina, 1984, et al.
(författare)
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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
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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)
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10 dB small-signal graphene FET amplifier
- 2012
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 48:14, s. 861-863
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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)
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Noise Figure Characterization of a Subharmonic Graphene FET Mixer
- 2012
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Ingår i: IEEE MTT-S International Microwave Symposium Digest. - 0149-645X. - 9781467310871
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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)
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Resistive Graphene FET Subharmonic Mixers: Noise and Linearity Assessment
- 2012
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 60:12, s. 4035-4042
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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
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Ingår i: ECS Transactions. - : The Electrochemical Society. - 1938-5862 .- 1938-6737. ; 80:1, s. 157-176
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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)
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High-Gain Graphene Transistors with a Thin AlOx Top-Gate Oxide
- 2017
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322 .- 2045-2322. ; 7:1
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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)
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A 30-GHz Integrated Subharmonic Mixer based on a Multichannel Graphene FET
- 2013
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Ingår i: IEEE Transactions on Microwave Theory and Techniques. - 0018-9480 .- 1557-9670. ; 61:2, s. 841-847
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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)
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A Large Signal Graphene FET Model
- 2012
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Ingår i: IEEE Transactions on Electron Devices. - 1557-9646 .- 0018-9383. ; 59:4, s. 968-975
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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)
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A subharmonic graphene FET mixer
- 2012
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Ingår i: IEEE Electron Device Letters. - 0741-3106 .- 1558-0563. ; 33:1, s. 71-73
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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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