Dual-Gate Graphene FETs With $f_{T}$ of 50 GHz (original) (raw)

Dual-Gate Graphene FETs With fTf_{T}fT of 50 GHz

IEEE Electron Device Letters, 2010

A dual-gate graphene field-effect transistors is presented, which shows improved RF performance by reducing the access resistance using electrostatic doping. With a carrier mobility of 2700 cm 2 /Vs, a cutoff frequency of 50 GHz is demonstrated in a 350-nm gate length device. This f T value is the highest frequency reported to date for any graphene transistor, and it also exceeds that of Si MOSFETs at the same gate length, illustrating the potential of graphene for RF applications.

Development of graphene FETs for high frequency electronics

2009

Recent advances in fabricating, measuring, and modeling of top-gated graphene FETs for high-frequency electronics are reviewed. By improving the oxide deposition process and reducing series resistance, an intrinsic cutoff frequency as high as 50 GHz is achieved in a 350-nm-gate graphene FET at a drain bias of 0.8 V. This f T value is the highest frequency reported to date for any graphene transistor, and it also exceeds that of Si MOSFETs at the same gate length, illustrating the potential of graphene for RF applications.

Graphene RF Transistor Performance

2000

Recent excitement about graphene as a possible material for highfrequency electronics has lead to demonstrations of high-frequency field-effect transistors (FETs) in the last two years. Although graphene FETs operate by a different principle than silicon MOSFETs, and have different DC characteristics, their ac properties are quite similar. Hence the high intrinsic mobility of graphene leads to the expectation of high frequency operation of gated graphene FETs. Demonstrations of frequency response in the GHz regime have been shown using both exfoliated flakes and synthesized graphene. An intrinsic cut-off frequency as high as 100 GHz has been achieved in a 240-nm-gate graphene FET fabricated on a 2" wafer of epitaxially-grown graphene. This value exceeds that of Si MOSFETs at the same gate length, illustrating the potential of graphene for RF applications.

Operation of Graphene Transistors at GHz Frequencies

2008

Top-gated graphene transistors operating at high frequencies (GHz) have been fabricated and their characteristics analyzed. The measured intrinsic current gain shows an ideal 1/f frequency dependence, indicating an FET-like behavior for graphene transistors. The cutoff frequency fT is found to be proportional to the dc transconductance gm of the device. The peak fT increases with a reduced gate length, and

RF performance of short channel graphene field-effect transistor

2010

Introduction: Graphene, a two dimensional single sheet of carbon atoms with excellent electronic properties, has attracted tremendous research efforts because of its high carrier mobility and velocity . While the lack of a bandgap in graphene makes its use challenging for digital applications, significant progress has been made on graphene analog devices for radio-frequency (RF) applications, where a high on/off ratio is not necessarily required. Recently, graphene RF transistors [6-7] with a cut-off frequency as high as 100 GHz have been demonstrated . Future advances in the RF performance would rely on the proper scaling of the graphene channel. Despite extensive theoretical efforts, a systematic experimental scaling study has been largely lacking. In this paper, we present experimental studies on transport characteristics of graphene FETs with channel lengths down to 70 nm. The factors limiting the performance of short channel graphene devices are discussed. RF performance of a sub-100 nm graphene transistor fabricated on epitaxial graphene grown on a SiC substrate is also presented. A cut-off frequency as high as 170 GHz is achieved in a 90 nm graphene FET using a scalable top-down fabrication processes. Our results indicate that further improvement of RF performance of graphene FETs can be enabled by channel length scaling with structure optimization and contact resistance reduction. Experiments: 20nm Pd/30nm Au by e-beam evaporation is used as the contact metal. NFC/HfO2 is used as the top gate dielectric for top-gated RF devices . Results and discussion: The carrier density dependence of the total resistance of a 1µm and a 70 nm device at V ds =10 mV at room temperature is shown in . The mobility can be extracted by model fitting . The quantum capacitance and the impact of gate field on contact resistance are not considered here. and show the output characteristics of the 1µm and 70 nm device at room temperature and low temperature. summarizes the temperature-dependent transfer characteristics for the 70 nm device. The transconductance is increased by almost 40% when measured at low temperature as shown in summarizes the temperature dependence of carrier mobility. The decrease of effective mobility as the channel gets shorter is a strong signature of quasi-ballistic transport. . summarizes the temperature dependent contact resistance of the three different devices. The reduction of contact resistance would greatly benefit the DC and RF performance, especially for short channel devices. In order to evaluate the performance of short channel graphene devices for RF applications, a "virtual source" model, which was originally developed for Si MOSFET [9], is adopted here after incorporating the effect of residual doping at the Dirac point, drain-induced doping effect

Field controlled RF Graphene FETs with improved high frequency performance

We propose a novel Graphene FET (GFET) with two capacitively coupled field-controlling electrodes (FCEs) at the bottom of the ungated access regions between gate and source/drain. The FCEs could be independently biased to modulate sheet carrier concentration and thereby the resistance in the ungated regions. The reduction of source/drain access resistance results in increased cut off frequency compared to those of conventional GFETs with the same geometry. We studied the DC and improved RF characteristics of the proposed device using both analytical and numerical techniques and compared with the baseline designs.

RF Performance Projections of Graphene FETs vs. Silicon MOSFETs

2011

A graphene field-effect-transistor (GFET) model calibrated with extracted device parameters and a commercial 65 nm silicon MOSFET model are compared with respect to their radio frequency behavior. GFETs slightly lag behind CMOS in terms of speed despite their higher mobility. This is counterintuitive, but can be explained by the effect of a strongly nonlinear voltage-dependent gate capacitance. GFETs achieve their maximum performance only for narrow ranges of V DS and I DS , which must be carefully considered for circuit design. For our parameter set, GFETs require at least µ=3000 cm 2 V -1 s -1 to achieve the same performance as 65nm silicon MOSFETs.

RF DEVICE CHARACTERIZATION OF GRAPHENE TRANSISTORS

ProQuest, 2023

Radio Frequency performance of field-effect transistors has been explored in depth, experimented and industrially in use since a long time. Whenever one thinks of transistors which could take us to the regime of more than 1 THz in frequency it would always be the High Electron Mobility Transistors (HEMTS) as the perfect solution to that. The Graphene transistors have been very much in research from 2010 and promise equal results due to their huge potential in mobility. In the Semiconductor Manufacturing And Fabrication Laboratory at the Rochester Institute Of Technology our research group has been designing, fabricating and characterizing the graphene transistors of top-gated and back- gated varieties of which the former has been more explored and characterized because of its potential in high frequency performance. In this thesis characterization of both the top-gated and the back-gated varieties will be discussed in intricate detail with different permutation and combinations in experiments in order to depict the efficiency of these transistors in terms of their frequency characteristics and the possible ways to optimize the mobility and transconductance, thereby changing the hysteresis behaviours of the top-gated transistors. The maximum oscillation frequency has been explored for the top- gated variant where it can be estimated how they are in performance and exhibit unique nature compared to that of the PMOS and the NMOS devices along with this distinctive hysteresis behaviours by application of a polymer on GFETs has been investigated.

100-GHz Transistors from Wafer-Scale Epitaxial Graphene

Science, 2010

High-performance graphene field-effect transistors have been fabricated on epitaxial graphene synthesized on a two-inch SiC wafer, achieving a cutoff frequency of 100 GHz for a gate length of 240 nm. The high-frequency performance of these epitaxial graphene transistors not only shows the highest speed for any graphene devices up to date, but it also exceeds that of Si MOSFETs at the same gate length. The result confirms the high potential of graphene for advanced electronics applications, marking an important milestone for carbon electronics.

Insights on radio frequency bilayer graphene FETs

IEDM 2012 Technical Digest, 2012

In this work, we investigate through atomistic simulations the possible improvements achievable by using bilayer graphene as FET channel material for radio frequency applications, and the related challenges. Bilayer graphene shows better performance as compared to monolayer graphene in terms of larger output resistance, which in turns is beneficial both for the low frequency voltage gain, and the maximum gain frequency.