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     

Micrometre-gate m.e.s.f.e.t.s on laser-annealed polysilicon

Schottky-barrier field-effect transistors (m.e.s.f.e.t.s) have been fabricated on uniformly doped laser-annealed polycrystalline silicon deposited on a silicon nitride insulator. The devices, which had aluminium Schottky-barrier gates and diffused n+ sources and drains but nonoptimised channel profiles, had about 65% the gm values of similar but optimised devices made on s.o.s. layers. Performance of these devices is considered adequate for certain innovative integrated-circuit technologies.     

Substrate dependence of InP m.e.s.f.e.t. performance

There is evidence to suggest that Fe outdiffuses, during the growth, into the epitaxial films prepared by vapour-phase epitaxy at 650°C. Field-effect transistors on Fe-doped material show substantial looping that was absent on Cr-doped material and exhibit about 2 dB worse noise figure at about 7 GHz. Experiments with low 1015 S-doped InP grown on Sn-, Cr- and Fe-doped substates indicate that such outdiffusion is typically about 5 ?m. Saturation velocity levels in the m.e.s.f.e.t. channel are about 1.7 × 107 cm/s and 1.3 × 107 cm/s, associated with Cr and Fe doped substrates, respectively.     

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.     

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.     

Mobility, transit time and transconductance in submicrometre-gate-length m.e.s.f.e.t.s

Two-dimensional simulations of submicrometre-gate-length m.e.s.f.e.t.s of Si, GaAs and InP show that device transit time and transconductance depend more on high-field diffusion constant and the shape of the velocity/field characteristic than on low-field mobility. Reasonable InP devices have shorter transit times and higher transconductances than GaAs devices, and for certain device parameters these figures of merit can be almost the same for Si and GaAs devices.     

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.     

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.     

Applications of dual-gate GaAs m.e.s.f.e.t.s for fast pulse shape regeneration systems

The suitability of dual-gate GaAs m.e.s.f.e.t.s for pulse shape reconstruction in the Gbit/s range is presented. The properties of these f.e.t.s and the circuitry for reduction of pulse width and pulse slope are both described. The variation of the input/output pulse-width ratio and the time behaviour for fast pulses are shown.     

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.     

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.     

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.     

New estimate of the minimum noise figure of a m.e.s.f.e.t.

New estimates of the drain and gate noise multiplication parameters, the correlation coefficient and the minimum noise figure for a m.e.s.f.e.t. are advanced. For an uncooled GaAs m.e.s.f.e.t. having a 1 ?m gate length, a minimum possible noise figure of 1 dB at 10 GHz is predicted. InP is only marginally better.     

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.     

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.     

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.     

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.     

Leak-compensated analog memory with pair m.o.s.f.e.t.s

A fast, simple, and relatively stable analog memory element is proposed, composed of two condensers and a pair of complementary m.o.s.f.e.t.s. The memory element was made sufficiently stable by the use of complementary m.o.s.f.e.t.s to enable a learning machine to complete the learning process within a comparatively short time.     

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.