Publisher Summary This chapter examines the signal and noise properties of gallium arsenide (GaAs) microwave field-effect transistors (FET) High frequency gallium arsenide field-effect transistors (GaAs FETs) have demonstrated remarkably low noise figures and high power gains at microwave frequencies A practical microwave GaAs FET is usually fabricated by deposition or diffusion of source, gate, and drain contacts on the surface of an appropriately doped thin epitaxial n-type layer This layer, in turn, is grown on a semi-insulating wafer by either a vapor or liquid epitaxial technique The apparent minor role played by the negative resistance region in practical short-gate FETs suggests that radiofrequency instabilities due to this region, if they exist, occur at frequencies far above the normal frequency regime of microwave FETs The small-signal equivalent circuit of the FET, valid up to moderately high frequencies is elaborated It is found that noise in a microwave GaAs FET is produced both by sources intrinsic to the device and by thermal sources associated with the parasitic resistances

Signal and Noise Properties of Gallium Arsenide Microwave Field-Effect-Transistors

A survey is given of the most important noise problems in solid-state devices. Section II discusses shot noise in metal-semiconductor diodes, p-n junctions, and transistors at low injection; noise due to recombination and generation in the junction space-charge region; high-level injection effects; noise in photodiodes, avalanche diodes, and diode particle detectors, and shot noise in the leakage currents in field-effect transistors (FETs). Section III discusses thermal noise and induced gate noise in FETs; generation-recombination noise in FETs and transistors at low temperatures; noise due to recombination centers in the space-charge region(s) of FETs, and noise in space-charge-limited solid-state diodes. Section IV attempts to give a unified account of 1/f noise in solid-state devices in terms of the fluctuating occupancy of traps in the surface oxide; discusses the kinetics of these traps; applies this to flicker noise in junction diodes, transistors, and FETs, and briefly discusses flicker noise in Gunn diodes and burst noise in junction diodes and transistors. Section V discusses shot noise in the light emission of luminescent diodes and lasers, and noise in optical heterodyning. Section VI discusses circuit applications. It deals with the noise figure of negative conductance amplifiers (tunnel diodes and parametric amplifiers), and of FET, transistor, and mixer circuits. In the latter discussion capacitive up-converters, and diode, FET, and transistor mixers are dealt with.

Noise in solid-state devices and lasers

A review of recent and current work on microwave FET's and amplifiers is presented, and an extensive bibliography of recent articles is appended (250 references). First, the various FET structures (MRSFET's, JFET's, and IGFET's) and their performances are reviewed. Second, the principle of operation is outlined for Si- and GaAs-MESFET's; the basic device physics, equivalent circuit, high-frequency limitations, and noise behavior are treated. Third, the design principles and performance of microwave MESFET amplifiers are summarized.

Microwave Field-Effect Transistors--1976

The microwave properties of silicon Schottky-barrier field-effect transistor(MESFET'S) with a gate-length of one micrometer are investigated. The scattering parameters of the transistors have been measured from 0.1 GHz up to 12 GHz. From the measured data an equivalent circuit is established which consist of an intrinsic transistor and extrinsic elements. Some of the elements of the intrinsic transistor, notably the transconductance, are strongly influenced by the saturation of the drift velocity. Best performance of the intrinsic transistor is obtained with highly doped and thin channels. The measured power-gain is in good agreement with theoretical values deduced from the equivalent circuit. The best device has a maximum frequency of oscillation fmax of 12 GHz. The investigation reveals that the extrinsic elements, especially the resistance of the gate-metallization and the gate-pad parasitics, degrade the power-gain considerably. Without them a value of fmax close to 20 GHz is predicted.

Microwave properties of Schottky-barrier field-effect transistors

Small signal and noise characteristics for GaAs field-effect transistors are derived with the saturated drift velocity of the carriers underneath the gate taken into account. The noise contributed by the saturated carriers is nonnegligible and in most cases, exceeds the noise generated by the unsaturated region. Parasitic elements contribute importantly by preventing the full cancellation of the correlated noise of the intrinsic transistor and by adding their own Johnson noise. The theory predicts the experimentally observed trend of noise figure dependence on drain current and on source-to-drain voltage. The present theory doesnot take into account the effects of a possible short negative resistance region underneath the gate.

Noise characteristics of gallium arsenide field-effect transistors

In this theory a field-effect transistor of planar geometry is considered as an active, distributed, nonuniform transmission line. The wave equation of this line is determined and solved by an approximation method. From this solution the y parameters are determined. By comparing the results for y 11 with van der Ziel's expression for the high-frequency gate noise of field-effect transistors, it is shown that the noise temperature of y 11 is of the order of the device temperature. The conductance part g 11 of y 11 varies as ω2over a wide frequency range. The high-frequency cutoff of the field-effect transistor is determined.

J.W. Ero

Papers

Small-signal, high-frequency theory of field-effect transistors