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.     

Subthreshold behaviour of e.s.f.i.-s.o.s. transistors

Theoretical and experimental results are presented which illustrate the influence of various parameters on the subthreshold behaviour of e.s.f.i.-s.o.s. transistors. The numerical analysis accounts for the thin silicon film and the existence of a second interface. A comparison is made with a corresponding bulk transistor, furthermore, between a two- and a one-dimensional analysis of e.s.f.i.-s.o.s. m.o.s.t. The agreement for real cases is found to be excellent.     

Optimised doping profiles for speed-up of GaAs m.e.s.f.e.t.s

Simulation of m.e.s.f.e.t. logic cell shows that discharging of the gate depletion is significantly slower than the charging process. The transient response with the charging/discharging is analytically connected to arbitrary doping profiles. Specific profiles with a doping peak near the substrate boundary can reduce this discharging delay remarkably.     

Current-kink noise of n-channel enhancement e.s.f.i.-m.o.s. s.o.s. transistors

An experimental study of the low-frequency-noise properties of n-channel epitaxial silicon films on insulator m.o.s. s.o.s. transistors has been performed. The measurements show an excessive noise contribution at drain voltages corresponding to the current-kink effect for temperatures ranging from 4.2 to 300 K.     

GaAs gigabit logic circuits using normally-off m.e.s.f.e.t.s

Normally-off GaAs m.e.s.f.e.t. logic circuits fabricated by electron beam lithography have exhibited excellent high speed switching characteristics. The highest switching speed evaluated from a 15-stage ring oscillator is 30 ps per gate with a power dissipation of 1.9 mW. Binary frequency dividers have been fabricated with D-type flip-flops operating up to 3 GHz. A divide-by-eight counter has also operated at 2.5 GHz.     

Semi-ideal sine oscillators (s.i.s.o.)

A class of semi-ideal sine oscillators (s.i.s.o.) featuring independent control of frequency and damping and lack of spurious responses is described.     

New n-channel m.o.s.f.e.t.s

By using plasma c.v.d. and lift-off, an n-channel m.o.s.f.e.t. with effective channel length of 0.4 ?m has been fabricated. Its main fabrication processes and obtained electrical characteristics are described.     

Voltage controlled monolithic s.a.w. phase shifter using m.z.o.s. structure

A monolithic surface-acoustic-wave (s.a.w.) phase shifter, fabricated with sputtered zinc oxide on an oxidised n silicon substrate, is demonstrated. Almost 67° of voltage controlled phase shift is achieved in 200 acoustic wavelengths of interaction region at 214 MHz.     

Maximum-likelihood method for identifying linear s.i.s.o. systems

A routine is described which uses the maximum-likelihood method to fit a discrete transfer-function model to a single-input single-output linear dynamic system. The algorithm is identical to the well known Astrom-Bohlin procedure.     

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.     

Improvements for general-purpose s.s.i. logic packages and m.s.i./l.s.i. logic subsystems

Various specifications for general-purpose logic packages for random-logic design use have been previously proposed. Current research interests in more powerful logic design techniques, however, are suggesting newer s.s.i. integrated-circuit packages for future use, and newer and more compact subsystems within future m.s.i./l.s.i. logic packages.     

Error-rate measurements for s.f.s.k. with band limitation

The error rates of s.f.s.k. with matched-filter detection were measured under restricted bandwidth conditions. The Eb/N0 degradations from the ideal b.p.s.k. performance were determined as a function of the degree of band limitation. Results for both Gaussian and Butterworth filters are presented.     

Effects of capacitance at crossover wirings in power GaAs m.e.s.f.e.t.s.

Power GaAs f.e.t.s. with an air-bridge crossover were compared with those of SiO2 crossover to find the effect of the capacitance at the crossover points. The capacitance of SiO2 crossover points is much smaller than that of the gate pad or the gate busbar in power GaAs f.e.t.s, and deterioration of the microwave performance due to that capacitance is negligible.     

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.     

Depletion-type m.o.s.f.e.t.s for low-temperature operation

Taking carrier freeze-out into account|a novel structure for depletion-type m.o.s.f.e.t.s suitable for low-temperature operation is proposed. Its channel consists of two regions; a relatively wide, low-impurity-density region and a relatively narrow, high-impurity-density region. It is estimated that the proposed structure has more square-law-like load character istics and higher current density than conventional ones.     

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.     

New s.a.w. time-inversion system

A new s.a.w. time-inversion system is described. It requires fewer chirp-filter elements than those required with the common method of cascading two Fourier or Fresnel transformations. This new method is based on the fact that the Fourier transform of a linear f.m. signal whose envelope is modulated by a given time function has (approximately) the time-inverted function as its amplitude. Theoretical discussion and some experimental results are included.     

Polarisable dielectrics for m.o.s.t.s

The use of a new and polarisable dielectric layer has made it possible to obtain large threshold-voltage shifts in m.o.s. capacitors.     

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.