The channel length and width of fabricated GFET are 9. The length of TG is 2. The white dotted frame shows location of the single layer graphene. Scanning electron microscopy SEM image of the device surface is displayed in Fig.
The boundary of the buried graphene layer can be discovered with easiness because of high electrical conductivity of graphene. The inset shows relationship between location of the newly formed Dirac point and TG voltages and illustrates that new Dirac voltage is approximately a linear function of TG voltage, which agrees well with equation 9. With decrease of TG voltage, an increasing number of holes will be injected into the graphene layer underneath TG due to capacitance effect, which results in decrease of the doping level of graphene.
In other words, the total area of the soft n-doped graphene increases with decrease of V TGS. Therefore, resistance of this part graphene plays a growing important role in the total channel resistance. The reason is that TG can dope the graphene near the TG edges due to edge effect of the capacitor structure and the total doping range increases when V TGS decreases increase in absolute value. Nonlinear behaviour in the inset at lower V TGS is another result of edge effect proposed above.
Therefore, with narrow TG for underneath graphene electrostatic doping, obvious inhomogeneous graphene could be formed in the FET channel and a W-shaped transfer curve was obtained with dual-gated GFET. The capacitor C from a bias tee was used to block the DC signal from the output V out. In other words, a higher symmetrical factor in the working area can result in a higher output power of the fourth harmonic.
The relative output RF power spectrum is obtained through the Fourier transform of the output real time RF signals. In order to investigate the RF conversion efficiency of the frequency quadrupler, the RF input power was obtained. The quadrupled output power is 2.
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Here, noticeably for the first time a GFET based frequency quadrupler is reported. Moreover, the simple dual-gated GFET based frequency quadruplers provide perfect illustration of versatility of graphene material once again. A frequency multiplier with simple structure and tunable multiplication factor may have lots of superiorities for RF electronic applications due to low cost and high integration.
In our case, dual-gated GFET can also work as high performance frequency doublers or frequency triplers with a suitable operation area.
Therefore, dual-gated GFET can work as high performance frequency doublers, frequency triplers and frequency quadruplers by choosing suitable operation areas. This is the first time that a multi-mode frequency multiplier is reported. With potential ultrahigh carrier mobility and high saturation velocity, graphene can response to high frequency signals completely. Hence large RC time constant of the device structure is major obstacle to improvement of operation bandwidth of graphene based device.
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Therefore, performance of graphene based devices can be enhanced significantly if an optimized fabrication process is carried out to decrease both parasitic capacitance and output resistance. More clearly, in order to decrease the parasitic capacitance of the GFET-based frequency quadrupler, a highly resistive substrate such as quartz assisting with a local BG technique is preferred.
On the other hand, both contact resistance and channel resistance make contribution to output resistance of GFET. A polymeric residue-free graphene fabrication process 50 can be carried out to reduce contact resistance. In order to investigate limitation of operation frequency of dual-gated GFET-based frequency quadrupler, a developed device structure is designed and proposed. With this structure, time constant of about 1. Hence graphene-based frequency quadruplers have great potential to generate ultrahigh frequency signals and could find its roles easily in ultrahigh frequency electronic applications in near future.
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A multi-mode frequency multiplier. The zero band gap of graphene enables tunable electronic transport polarity. In this work, a narrow top gate was utilized to dope underneath graphene with electrostatic field, and a tunable transfer curve was achieved with one GFET. With the tunable transfer curve, GFET can work as high performance frequency doubler, frequency tripler and frequency quadrupler.
High multiplication factor. Without any additional filter system, it is impossible to achieve a frequency multiplier with high multiplication factor by using traditional nonlinear electronic devices because output power of the high-order harmonic is much smaller than the low-order harmonic. With superhigh carrier mobility of graphene, this graphene-based frequency multiplier will play an important role in the ultrahigh-frequency electronic applications, such as signal generator for THz. Low cost. The cost-effective high performance CVD graphene material can be available with rapid improvement of the synthetic technology.
Simplicity of the GFET structure results in low fabrication cost. Furthermore, the demand of this multi-mode frequency multiplier increasing rapidly as communications would become indispensable nowadays. In summary, a novel dual-gated GFET based high performance frequency quadrupler is presented. Benefit from electrostatic doping effect of the narrow TG to the underneath graphene, a W-shaped transfer curve was obtained with only one GFET.
With this new type nonlinear I-V feature, a graphene-based frequency quadrupler was achieved. This device can also operate as high performance frequency doublers and frequency triplers. To the best of our knowledge, it is the first reported multi-mode graphene based frequency multiplier in the world. The potential ultrahigh carrier mobility of the graphene, together with simplicity of the device structure and CMOS compatible fabrication processes makes the dual-gated GFET based frequency quadrupler one of the most captivating candidates for future ultrahigh-frequency electronics, especially RF applications.
We characterized the fabricated device at room temperature in ambient conditions. How to cite this article: Cheng, C. A graphene based frequency quadrupler. Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Raisanen, A. Frequency multipliers for millimeter and submillimeter wavelengths. IEEE 80 , — Riley, J. Design considerations for an harmonic radar to investigate the flight of insects at low altitude.
Chien, G. IEEE J. Solid-State Circuits 35 , — Bao, M. A D-band keyable high efficiency frequency quadrupler. IEEE Microw. Wireless Compon. Chen, G. IEEE Trans. Theory Tech. Abbasi, M.
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Novoselov, K. Electric field effect in atomically thin carbon films. Science , — Bolotin, K. Ultrahigh electron mobility in suspended graphene. Solid State Commun. Nair, R. Fine structure constant defines visual transparency of graphene. Science , Wang, F. Gate-variable optical transitions in graphene. Lee, C.
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A graphene based frequency quadrupler | Scientific Reports
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