Bit synchronisation in Gbit/s range using dual gate GaAs m.e.s.f.e.t.s

Bit synchronisation at 1 and 2 Gbit/s including pulse width reduction is achieved using dual gate GaAs m.e.s.f.e.t.s. Circuits and time behaviour of input-, clock- and output signals are shown.     

GaAs m.e.s.f.e.t. technology and characteristics for optical communication systems

For pulse regeneration applications GaAs m.e.s.f.e.t.s with low pinch-off voltages are desirable. The technology and the dependence of the input/output pulse width ratio on the bias voltage are described. The pulse behaviour of a two-stage sharpener is shown and the block diagram of an optical repeater station is proposed.     

Multi/demultiplexing in Gbit/s range using dual gate GaAs m.e.s.f.e.t.s

Multiplexing from 1 to 2 Gbit/s and corresponding demultiplexing from 2 to 1 Gbit/s including clock regeneration and pulse width reduction has been performed using dual gate GaAs m.e.s.f.e.t.s. Circuits and time behaviour of input, clock and output signals are shown.     

Circuit model for the GaAs m.e.s.f.e.t. valid to 12 GHz

A new equivalent circuit is given for the GaAs m.e.s.f.e.t., which includes resistive loss in the feed back elements. The circuit values are given for several 1 ?m-gate GaAs m.e.s.f.e.t.s. A method for fitting s12 to the measured data is described. Finally, the gain and stability factor of several GaAs m.e.s.f.e.t.s. are extrapolated to 24 GHz from the present model.     

Conversion gain of m.e.s.f.e.t. drain mixers

A theoretical analysis of the gain properties of m.e.s.f.e.t. drain mixers is presented. The m.e.s.f.e.t. model includes the nonlinearity of both the transconductance and the drain resistance. For a special case, a simple analytical expression for the gain is given. Numerical results for a typical example are briefly presented as an illustration.     

GaAs power f.e.t.s with semi-insulated gates

GaAs semi-insulated-gate f.e.t.s (s.i.g.f.e.t.s) have been fabricated by Ar+ bombardment in the gate region. The d c. characteristics and microwave performance are compared with those of conventional power m.e.s.f.e.t.s fabricated from the same slice. Up to 2.9W output power with 4dB gain has been obtained from s.i.g.f.e.t. devices at 8 GHz.     

Simplified GaAs m.e.s.f.e.t. model to 10 GHz

A simplified design-oriented equivalent circuit for the GaAs m.e.s.f.e.t. is presented. Its relation to a common, but more complex, model is derived and characteristics are compared. Element values are easily determined from measurements, and the simple model shows good agreement with measured parameters to 10 GHz for 1 ?m-gate m.e.s.f.e.t.s.     

I.C.-compatible completely planar GaAs m.e.s.f.e.t.s. by selective diffusion

Completely planar GaAs m.e.s.f.e.t.s were produced by selective open tube diffusion from tin-doped spin-on SiO2 films. After the diffusion process no change in the surface morphology was observed in the doped regions. The evaluation of saturation currents of the m.e.s.f.e.t.s show very good homogeneity. Isolation between doped areas was excellent. Sample preparation and device results are presented; possible applications are outlined.     

High-speed 1 ?m GaAs m.e.s.f.e.t.

By minimising parasitic series resistances, a GaAs m.e.s.f.e.t. with 1 ?m gate length was fabricated, possessing the highest known r.f. power gain, measured up to 18 GHz, for GaAs m.e.s.f.e.t.s.     

Direct modulation of d.h. GaAlAs lasers with GaAs m.e.s.f.e.t.s

GaAs m.e.s.f.e.t.s are used to directly modulate d.h. GaAlAs lasers with a 200 Mbit/s pseudorandom, return-to-zero bit stream. The detected light pulses have 100% modulation depth, no significant intersymbol interference, 40 mW of peak power and risetimes and falltimes of 240 ps for a halfpower width of 280 ps.     

V-shaped-gate GaAs m.e.s.f.e.t. for improved high-frequency performance

The idea of gate shaping in f.e.t.s was implemented into the GaAs-m.e.s.f.e.t. structure. A m.e.s.f.e.t. with 2 ?m gate length was fabricated, the measured m.a.g. data of which allow an extrapolation to an fmax of about 45 GHz.     

Low-noise GaAs m.e.s.f.e.t.s

GaAs m.e.s.f.e.t.s with optimum noise figures of 1.6 dB at 6 GHz have been fabricated by projection photolithography. An equation has been developed for the calculation of optimum noise figure which gives good agreement between calculated and measured values.     

n-channel inversion-mode InP m.i.s.f.e.t.

Capacitance/voltage and m.i.s.f.e.t. inversion-mode f.e.t. data are reported for p-type InP. It is shown that the surface of this material appears to be inverted at zero gate bias and that good inversion-mode (normally-off) device behaviour is possible.     

Substrate conduction in GaAs m.e.s.f.e.t.s

Substrate currents in a gateless GaAs m.e.s.f.e.t. have been measured at d.c, 0.9 MHz and 2 GHz. The results are consistent with the assumption of substrate conduction at high frequencies and active-layer conduction alone at low frequencies.     

Remediable and nonremediable causes of parasitic elements in InP m.e.s.f.e.t.s

Two-dimensional analyses of InP and GaAs m.e.s.f.e.t. structures are used to qualitatively explain relative magnitudes of parasitic element values observed in experimental InP m.e.s.f.e.t.s. Large drain-gate capacitance observed in InP is attributed mainly to substrate conduction, whereas large drain conductance at certain drain biases in InP may be unavoidable due to large velocity dropback and large high-field diffusion in this material. Low Schottky-barrier height and substrate conduction also increase gD     

Low-noise microwave f.e.t.s fabricated by molecular-beam epitaxy

The growth of m.b.e. GaAs suitable for f.e.t. fabrication is reported. The m.b.e. structure consists of an n+ = 2.5×1018 cm?3 contact layer on top of an n+ = 3.5×1017 cm?3 active layer. Using this material, f.e.t.s. have been fabricated that have a minimum noise figure of 1.5 dB with an associated gain of 15 dB at 8 GHz. These are the best results yet reported for low-noise m.b.e. GaAs f.e.t.s.     

Femtojoule logic circuit using normally-off GaAs m.e.s.f.e.t.s

Experimental results are reported on the speed/power performance of normally-off-type GaAs-m.e.s.f.e.t. logic circuits, using an integrated 15-stage ring oscillator as a test circuit. A power consumption as low as 1-5 ?W, corresponding to a power-delay product of 1.6 fJ, was obtained. Conversely, a propagation delay time of 650 ps was measured for a power consumption of 20 ?W per gate.     

n- and p-channel m.o.s.f.e.t.s as Rayleigh-surface-wave detectors

We have studied the piezoresistance effect in an m.o.s.f.e.t. structure used as a Rayleigh-surface-wave transducer. The investigation was carried out over a large frequency range about a central value of 100 MHz. Results for silicon?m.o.s.f.e.t. n- and p- channel inversion layers are given.     

X and Ku band GaAs m.e.s.f.e.t.

A GaAs Schottky-barrier f.e.t. (m.e.s.f.e.t.) with a 1 ?m gate has been built, which is suitable for X band and Ku band applications. The unilateral power gain over the X band is above 9 dB and the noise figure is only 5 dB at 10 GHz.     

Performance of GaAs power m.e.s.f.e.t.s

Power performance results at 4 GHz are summarised for GaAs m.e.s.f.e.t.s ranging in size from 4 to 16 mm gate periphery. A double-chip 16 mm unit operated at 24 V source-drain bias produced 13.5 W with 3 dB gain and 10.7 W with 8.1 dB gain. Although lack of perfect power and gain scaling is observed, the degradation in output power of the 16 mm devices was only 1 dB compared to the smaller devices.