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The measurement of high dielectric constants materials in a coaxial line, using an automatic network analyser (ANA), must take the actual diameter of the sample into consideration. The error on the measured &Vegr;r value may be approximated by the fractional diameter deviation times &Vegr;r7. A correction method is proposed.

High repetition rate picosecond pulses with low uncorrelated timing jitter (down to ~0.25 ps) have been generated at 1.55 µm from gain- and Q-switched InGaAsP lasers without external feedback. Experiments were carried out at multi-gigahertz frequencies on one- and two-section devices; the timing jitter was estimated from spectral measurements. Sub-picosecond values were found above ~5 GHz for optimally-biased one-section DFB lasers in gain-switching. Values more than two times lower were obtained from Q-switched quantum well two-section lasers, with RF modulation applied to a fast absorber section.

HEMT electrostatic capacitances are determined with a 2-D finite element solver according to the device geometry. The calculation is compared with measurements on recessed ultrasubmicrometre rectangular gate and T-gate pseudomorphic and standard HEMTs on GaAs.

When coplanar probes are used, the open circuit reflection standard in the SOLT calibration technique is usually the most questionable of the four. This standard is described in the ‘cal kit’ as a capacitance, the value of which is determined in a ‘cut and try’ way. A more direct method is proposed in this Letter.

0.2μm Al0.48In0.52As/Ga0.47In0.53As LMHEMT on InP with an undoped GaInAs layer to reduce gate leakage have been realised and their DC and RF properties have been investigated cryogenic temperatures. The cutoff maximum frequencies oscillation Fmax up to 260 Hz are extrapolated at 50 K from the maximum unilateral gain (MUG) determined using S parameters measured up to 40 GHz. Evolution of gate leakage current and RF characteristics against gate and drain biases are presented between 50 and 300 K.

De-embedded high frequency (HF) noise parameters of Ge p-channel modulation doped field effect transistors (MODFETs) on a Si0.4Ge0.6 virtual substrate have been determined for the first time. The 0.1 × 100 µm devices have a minimum noise figure NFmin = 0.3 dB (0.5 dB) ± 0.2 dB, a noise resistance Rn = 95 Ω (90 Ω) ± 5 Ω, an optimum reflection coefficient Γopt = 0.7∠6° and an associated gain Gass = 14 dB (13 dB) at 1.2 GHz (2.5 GHz), at a bias corresponding to the optimum unity current-gain frequency fT = 55 GHz and the maximum oscillation frequency fMAX = 135 GHz. Noise results are given in the 1.2–12 GHz frequency range and 20–160 mA/mm current range.

RF and microwave noise performances of strained Si/Si0.58Ge0.42n-MODFETs are presented for the first time. The 0.13 µm gate devices have de-embedded fT = 49 GHz, fmax = 70 GHz and a record intrinsic gm = 700 mS/mm. A de-embedded minimum noise figure NFmin = 0.3 dB with a 41 Ω noise resistance Rn and a 19 dB associated gain Gass are obtained at 2.5 GHz, while NFmin = 2.0 dB with Gass = 10 dB at 18 GHz. The noise parameters measured up to 18 GHz and from 10 to 180 mA/mm with high gain and low power dissipation show the potential of SiGe MODFETs for mobile communications.

The authors report on RF results of p-type Ge channel modulation doped field effect transistors (MODFETs) with a gate length of 0.1 µm. The structure was grown on a relaxed 4.9 µm thick compositionally graded Si0.4Ge0.6 buffer. The devices exhibit DC transconductances up to 190 mS/mm and saturation currents up to 190 mA/mm. Cutoff frequencies of fT 59 GHz and fmax = 135 GHz have been obtained. The fmax value is, to the knowledge of the authors, the highest reported so far for p-type Si-based devices.

Modal decomposition in the time domain is shown to be applicable to lossy coupled transmission lines of equal width. It is rigorous for two lines and is a good approximation for more than two lines. This allows a direct time-domain simulation of buses made of microstrip lossy lines on chip or on board in digital circuits.

A large-signal model using a full transistor characterisation is developed for time-domain CAD of circuits. It uses 2-D look-up tables to describe the FETs nonlinear parameters which are a function of two internal voltages. It is validated in an experimental study of the step response of an NEC3SK MESFET.

A 50 Ω high frequency noise measurement has been developed. A new approach for calculating the four noise parameters is presented. This method necessitates no isolator and has broad-band capacities. Receiver calibration and F50 HEMTs measurements are presented.

A new high frequency noise measurement method has been developed for transistors based on the frequency dependence of the noise figure. Results for a 1 µm gate length MESFET are presented.

The electric parameter evolutions of state of the art ultrashort gate planar doped AlGaAs/GaAs HEMTs are studied against gatelength lg = 0.4–0.1 μm and bias. The best value of maximum intrinsic transconductance obtained is gm0max = 800mS/mm at lg = 0.15 μm and the measured cutoff frequency is ft = 125 GHz at lg = 0.1 μm.

AlGaAs/InGaAs/GaAs MODFETs having 20% indium in the channel and Si planar doping (5 × 1012cm-2) have been fabricated with gate lengths of 0.1–0.7μm and a width of 100μm. Gates that are longer than 0.2μm are T-shaped and the narrower gates (0.1 and 0.15μm) are triangular. From DC measurement a maximum Gm of 1100mS/mm has been obtained. The current gain cutoff frequency Ft corrected for the access resistances is 145 GHz, corresponding to an intrinsic transition frequency of 220 GHz.

A model of multiple lossy microstrip lines on IC chips or cards is developed for direct time domain simulation of interconnections at a low computational cost. It is concerned with lines of equal widths with losses independent of frequency. Measurements of the step response in the tens of picoseconds range of three coupled lines on GaAs validate the model in severe test conditions of strong ohmic losses.