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.     

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.     

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.     

U.H.F. low-noise GaAs m.e.s.f.e.t. amplifier for colour t.v. broadcasting translator

Low-noise amplifiers for u.h.f. colour t.v. broadcasting translator use have been successfully developed by using 1 ?m gate GaAs m.e.s.f.e.t.s. The obtained performances revealed that a GaAs m.e.s.f.e.t. has low-noise and low intermodulation distortion characteristics, even in the 500?800 MHz frequency range, compared with a Si bipolar transistor.     

14-GHz band 1 watt GaAs f.e.t. amplifier

A 14.0?14.5 GHz 1 W amplifier using 0.5 ?m gate length power GaAs f.e.t.s has been developed. The amplifier, consisting of a cascade of three single-ended stages, realises 13 dB small-signal gain, 1.1 W output-power saturation and 39 dBm third-order intermodulation intercept. The circuit design and the microwave performance of the amplifier are discussed.     

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.     

Extending the low-frequency range of GaAs f.e.t. broadband microwave amplifiers using microstrip transmission lines

A new microwave circuit technique is introduced to extend the frequency range of high-frequency GaAs m.e.s.f.e.t.s into the neighbourhood of 2 GHz so that wide-band amplifiers may be developed. The negative-feedback technique reduces |s11| sufficiently yet allows the other s-parameters to remain approximately the same, permitting the design of high-performance wide-band amplifiers. One such design is discussed.     

Microwave capability of 1.5 ?m-gate GaAs m.o.s.f.e.t.

1.5 ?m-gate GaAs m.o.s.f.e.t.s have been fabricated by anodic oxidation, and the microwave capability has been examined. The maximum oscillation frequency fmax is 22 GHz and the noise figure is 6.1 dB at 8 GHz. The results are comparable to those of GaAs m.e.s.f.e.t.s.     

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.     

High-yield self-alignment method for submicrometre GaAs m.e.s.f.e.t.s

A high-yield self-alignment technique for submicrometer GaAs m.e.s.f.e.t.s is described. This method allows the production of submicrometre gate lengths and source-drain spacings by means of standard contact photolithography without requiring a particularly fine geometry on the masks. A 0.5 ?m long gate and a source-drain spacing of 2 ?m were obtained.     

Enhancement-mode GaAs m.o.s.f.e.t. on semi-insulating substrate using a self-aligned gate technique

A self-aligned gate notched channel GaAs m.o.s.f.e.t. structure on semi-insulating substrate is presented. Device operation is mainly in enhancement mode. The transconductance is comparable to enhancement-mode m.e.s.f.e.t.s, j.f.e.t.s and s.i.g.f.e.t.s; however, the output-current capability is essentially increased.     

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.     

Large signal GaAs m.e.s.f.e.t. model and distortion analysis

A simple large signal model, derived from small signal measurements over a range of bias points, is presented for a 2 ?m gate length GaAs m.e.s.f.e.t. Its accuracy is verified by comparing model-predicted second harmonic distortion via time domain and Volterra analyses, with measurements to input frequencies of 4.5 GHz.     

High peripheral power density GaAs f.e.t. oscillator

Peripheral power density (p.p.d.), i.e. the output power per Unit gate width is defined as a figure of merit for GaAs f.e.t. oscillators. An X-band oscillator circuit using series and shunt feedback is described and its performance characteristies indicated. It is shown that this GaAs f.e.t. oscillator circuit configuration has the highest peripheral power density.     

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     

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.     

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.     

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.     

Noise behaviour of the m.o.s.f.e.t. at v.h.f. and u.h.f.

The optimum noise figures of an m.o.s.f.e.t. at u.h.f. and at pinch-off are calculated using a simplified equivalent circuit. The noise parameters are also determined experimentally. Theory and experiment are shown to be in good agreement. Noise parameters of the m.o.s.f.e.t. for the frequency range 0.1?0.8 GHz are given.