Gilles Dambrine

Flexible Gigahertz Transistors Derived from Solution-Based Single-Layer Graphene

Flexible electronics mostly relies on organic semiconductors but the limited carrier velocity in polymers and molecular films prevents their use at frequencies above a few megahertz. Conversely, the high potential of graphene for high-frequency electronics on rigid substrates was recently demonstrated. We conducted the first study of solution-based graphene transistors at gigahertz frequencies, and we show that solution-based single-layer graphene ideally combines the required properties to achieve high speed flexible electronics on plastic substrates. Our graphene flexible transistors have current gain cutoff frequencies of 2.2 GHz and power gain cutoff frequencies of 550 MHz. Radio frequency measurements directly performed on bent samples show remarkable mechanical stability of these devices and demonstrate the advantages of solution-based graphene field-effect transistors over other types of flexible transistors based on organic materials.

A new method for on wafer noise measurement

A method for measuring the noise parameters of MESFETs and HEMTs is presented. It is based on the fact that three independent noise parameters are sufficient to fully describe the device noise performance. It is shown that two noise parameters, R/sub n/ and mod Y/sub OPT/ mod , can be directly obtained from the frequency variation of the noise figure F/sub 50/ corresponding to a 50 Omega generator impedance. By using a theoretical relation between the intrinsic noise sources as additional data, the F/sub 50/ measurement only can provide the four noise parameters. A good agreement with more conventional techniques is obtained. >

High-frequency four noise parameters of silicon-on-insulator-based technology MOSFET for the design of low-noise RF integrated circuits

An exhaustive experimental study of the high-frequency noise properties of MOSFET in silicon-on-insulator (SOI) technology is presented. Various gate geometries are fabricated to study the influence of effective channel length, gate finger width, and gate sheet resistivity on the four noise parameters. The high level of MOSFET sensitivity to the minimum noise matching condition is demonstrated. From experimental results, optimal ways to realize ultra low noise amplifiers are discussed. The capability of the fully depleted standard SOI CMOS process for realizing low-noise amplifiers for multigigahertz portable communication systems is shown.

Microscopic noise modeling and macroscopic noise models: how good a connection? [FETs]

Based on the active line concept, a novel approach for the calculation of the high frequency noise performance of field effect transistors (FET) is proposed. By using a simple analytical theory, the FET small signal equivalent circuit as well as the macroscopic noise sources and their correlation are calculated for different two-port terminations. Values of the usual dimensionless noise parameters P, R, C, gate noise temperature T/sub g/ and drain noise temperature T/sub d/ are then given and discussed. By comparison with a more realistic numerical modeling of the noise performance, the validity of the analytical noise model is discussed. The validity of Pospieszalskis noise model and its relations with Pucels one is emphasized. >

Influence of the gate leakage current on the noise performance of MESFETs and MODFETs

Abstract In this paper, the influence of the gate leakage current on the noise performance of MESFETs and MODFETs is investigated. Both a simple analytical model and a more realistic numerical model have been developed. It is shown that the noise performance is strongly dependent on the gate leakage current value, especially at low frequency. The theoretical results are discussed and compared with experimental ones.

High-Frequency Noise Performance of 60-nm Gate-Length FinFETs

In this paper, the first-ever published investigation on radio-frequency (RF) noise performance of FinFETs is reported. The impact of the geometrical dimensions of FinFETs on RF noise parameters such as the channel length, the fin width, as well as the fin number is analyzed. A minimum noise figure of 1.35 dB is obtained with an associated available gain of 13.5 dB at 10 GHz for Vdd = 0.5 V. This result is quite encouraging to bring solutions for future low-power RF systems.

Analog/RF Performance of Multichannel SOI MOSFET

In this paper, for the first time, we present a detailed RF experimental and simulation study of a 3-D multichannel SOI MOSFET (MCFET). Being different from the conventional planar technology, the MCFET features a total of three self-aligned TiN/HfO2 gate stacks fabricated on top of each other, allowing current to flow through the three undoped ultrathinned silicon bodies (UTBs). In other words, the operation of the MCFET is theoretically based on two UTB double-gate SOIs and a single-gate UTB fully depleted SOI (FDSOI) at the bottom. Using on-wafer S-parameters, the RF/analog figures-of-merit of an MCFET with a gate length of 50 nm are extracted and discussed. Thanks to the enormous transconductance (gm) and very low output conductance, the RF/analog performances of MCFET-voltage gain (A VI) and early voltage (V EA) are superior compared with that of the single-gate UTB-FDSOI. However, these advantages diminish in terms of transition frequency (fT), due to the large total input gate capacitances (C GG). This inspires the introduction of spacer engineering in MCFET, aiming at improving both C GG and fT. The sensitivity of the spacer length to the RF/analog performances is experimentally analyzed, and the performance optimization is validated using ac simulation. This paper concludes that optimized MCFETs are a serious contender to the mainstream MOSFETs including FinFETs for realizing future low-power analog applications.

Fabrication and characterization of low-loss TFMS on silicon substrate up to 220 GHz

This paper presents the results of the fabrication and characterization up to 220 GHz, of thin-film microstrip (TFMS) transmission-line structures. The transmission lines are fabricated on a low-resistivity silicon substrate (/spl rho/=10 /spl Omega/ /spl middot/ cm). TFMS lines with a thick dielectric layer (20 /spl mu/m of benzocyclobutene is used here) present losses of 0.3 dB/mm at 94 GHz and 0.6 dB/mm at 220 GHz. Thus, using this technology, it will be possible to develop monolithic microwave integrated circuits on a silicon substrate.

High microwave and noise performance of 0.17-/spl mu/m AlGaN-GaN HEMTs on high-resistivity silicon substrates

AlGaN-GaN high-electron mobility transistors (HEMTs) based on high-resistivity silicon substrate with a 0.17-/spl mu/m T-shape gate length are fabricated. The device exhibits a high drain current density of 550 mA/mm at V/sub GS/=1 V and V/sub DS/=10 V with an intrinsic transconductance (g/sub m/) of 215 mS/mm. A unity current gain cutoff frequency (f/sub t/) of 46 GHz and a maximum oscillation frequency (f/sub max/) of 92 GHz are measured at V/sub DS/=10 V and I/sub DS/=171 mA/mm. The radio-frequency microwave noise performance of the device is obtained at 10 GHz for different drain currents. At V/sub DS/=10 V and I/sub DS/=92 mA/mm, the device exhibits a minimum-noise figure (NF/sub min/) of 1.1 dB and an associated gain (G/sub ass/) of 12 dB. To our knowledge, these results are the best f/sub t/, f/sub max/ and microwave noise performance ever reported on GaN HEMT grown on Silicon substrate.

Wide- and narrow-band bandpass coplanar filters in the W-frequency band

This paper deals with the design of passive coplanar devices in the W-frequency band. As long as coplanar transmission lines are correctly dimensioned, analytical models based on quasi-TEM approximation can be used. Such models are associated with a correct definition of the reference planes at the junctions and employed for junction discontinuities, T- and cross-junctions. In order to validate these assertions, simulated and experimental data on classical quarter-wavelength shunt-stub filters are first presented. Then the design of traditional coupled-line filters is examined. The problems in terms of insertion loss associated with these kinds of narrow-band applications are discussed here. Minimization of insertion losses requires increasing the width of the strips. Consequently, the design becomes complex and modeling using transmission-line models less accurate. Nevertheless, as an optimization procedure is needed to tune the filter theoretically, such a very fast design method is necessary. Simulated and experimental results in the range 500 MHz to 110 GHz are compared throughout the paper.