Transferred Electron Amplifiers Research Articles

Comment on noise in transferred electron amplifiers

The noise in transferred electron amplifiers is usually attributed to thermal noise of the carriers in the two valleys and intervalley scattering noise. The latter is here interpreted as being due to carrier density fluctuations in the two valleys (partition noise), which, because of the difference in mobility in the upper and lower valleys, shows up as current noise.

Computer simulation of InP transferred-electron amplifiers for Ka-band

A displaced Maxwellian approach which includes relaxation effects is used to simulate small- and large-signal InP transferred-electron amplifiers operating in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ka</tex> -band. The devices considered are short-circuit stable; that is, they have a subcritical doping-length product. The performance of amplifiers having the usual n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -cathode contacts, and p-type notch-cathode contacts designed to produce a uniform electric field, are compared. It is found that the notch contacts have a moderate influence on small-signal characteristics, and a profound influence on large-signal performance. Small-signal bandwidths of 65 percent are predicted for both types of contacts. The saturation efficiency of amplifiers, biased at three times threshold, is much higher for the notch-contact device with values near 5 percent being predicted. The nonlinearity of the large-signal gain characteristic is shown to vary greatly as the frequency deviates from the optimum value.

Origins of intermodulation distortion in transferred-electron amplifiers

Computer simulations and experiments on cathode-notch transferred-electron amplifiers have been carried out to relate one source of intermodulation distortion to the shape of the velocity-field characteristic of GaAs. Other sources of nonlinearity are caused by signal-dependent phase relationships between current and voltage when space-charge propagation effects are important.

Design of transferred-electron amplifiers with good frequency stability

An experimental and theoretical investigation has been conducted into the frequency stability, with respect to temperature, bias voltage, and microwave power variation, of transferred-electron amplifiers with various doping profiles. Devices with a cathode doping-notch which is large enough to cause a flat electric-field distribution at the working point show the best frequency stability. This behavior is associated with the predominance of a frequency-independent negative-conductor behavior in this type of device.

Indium phosphide: a semiconductor for microwave devices

Since 1970, InP has been developed as a material for microwave oscillators and amplifiers, with most interest to date being taken in transferred-electron devices. the physics of electron transport and of transferred-electron oscillators is reviewed; the features of greatest practical significance are the high potential oscillator efficiency set by the peak-to-valley ratio, which is approximately 3·5, of the velocity/field curve; studies of cathode-contact effects which have led to oscillator efficiencies over 20% and the observation of limited-space-charge-accumulation (l.s.a.) mode operation. Consideration is also given to other less developed InP microwave components, including transferred-electron small-signal amplifiers which have given noise measures of 8 dB at 15 GHz, and field-effect transistors for which encouraging preliminary results have been obtained.

The noise measure of GaAs and InP transferred electron amplifiers

The noise measures of both GaAs and InP transferred electron amplifiers (TEA's) are calculated by a small-signal computer simulation for devices having a range of realistic doping profiles, some of which are designed specifically to limit the amount of free charge injected into the structure. Optimum values of average electric-field strength and carrier concentration times length product for minimum noise are shown to exist. The computed results differ not too greatly from those predicted by a simple analytical model where a uniform free carrier concentration and dc electric field are assumed. The lowest noise measures predicted are 7 dB for GaAs and 4 dB for InP if charge injection is suitably constrained. The computed results are compared with results reported in the literature.

On the large-signal behavior of transferred-electron amplifiers with a cathode notch

Transferred-electron amplifiers (TEA) are finding applications where medium powers are required as driving stages. Most work has been done up to now under small-signal conditions. The present paper describes theoretical results of a large-signal analysis. From this analysis, it appears that different large-signal behaviors of TEA devices can be associated with their corresponding dc field distribution. We compare, by computer analysis, the evolution of the large signal impedance with the RF driving signal for different doping profiles (different stationary fields) and give design figures to increase the device added power.

Multilayered structures of epitaxial indium phosphide

Oscillators with efficiencies over 20% at 15 GHz that have small temperature sensitivity, and transferred electron amplifiers that have less than 9 dB noise figures at 15 GHz have been made from epitaxial multilayers of indium phosphide. The techniques involved in growing and characterising these epitaxial layers are presented.

Theoretical characteristics of transferred-electron amplifiers

The general characteristics of transferred-electron amplifiers predicted by a computer solution of the electron Boltzmann equation include the ratio of the maximum to the minimum operating frequency of approximately 3 and an intrinsic Q factor of about 1. The variation of the impedance function with the device parameters is discussed.

Low-noise microwave amplification using transferred-electron and baritt devices

The small signal amplifying properties of both GaAs and InP transferred electron devices and of Si baritt devices are considered using simple physical models. InP is predicted theoretically to be capable of providing devices having the lowest noise measure. The paper shows that, for transferred-electron amplifiers, an optimum value of nl product exists for lowest noise measure.

The effect of cathode-notch doping profiles on supercritical transferred-electron amplifiers

The results of computer simulations are presented to describe the stabilization and amplification performance of supercritically doped transferred-electron devices that contain a cathode-conductivity notch. Broad agreement is found between the theoretical and experimental behavior. Nonlinear conversion of amplitude modulation (AM) to phase modulation (PM) is less than 5°/dB.

Design and performance of transferred electron amplifiers using distributed equalizer networks: IEEE J. of Solid State Circuits, Vol SC-8, No 1 (February 1972) pp 29–36

This paper describes improved techniques for the design of broad-band linear reflection-type microwave amplifiers using transferred electron devices. These techniques have produced excellent agreement between amplifier design goals and performance. This agreement results from improvements in measuring techniques and data reduction in addition to the use of a distributed equalizer topology. Multistage amplifiers having a net gain of over 25 dB and a power output in excess of 0.4 W over a bandwidth of 4 GHz in X- band have been realized.

An Experimental Study of Stabilized Transferred-Electron Amplifiers

Experimental data are presented to describe various characteristics of stabilized transferred-electron amplifiers. The effect of bias voltage upon RF gain and linearity is shown. The conditions under which gain expansion is observed are described, and the importance of lattice temperature and RF signal strength in determining dc current is shown. All results are shown to be in good agreement with the large-signal theory for these amplifiers.

On the mechanism for microwave amplification in ``supercritically'' doped n-GaAs

Good agreement is obtained between experiment and numerical calculations on supercritically doped n-GaAs transferred electron amplifiers. When moderate doping depletions near one electrode are included in the calculations, the results correctly predict the small-signal impedance and current-voltage characteristics, including the bias-induced stable-unstable-stable regimes. The results demonstrate the dominant role played by the electrodes in controlling the behavior of transferred electron amplifiers.

Design and performance of transferred electron amplifiers using distributed equalizer networks

This paper describes improved techniques for the design of broad-band linear reflection-type microwave amplifiers using transferred electron devices. These techniques have produced excellent agreement between amplifier design goals and performance. This agreement results from improvements in measuring techniques and data reduction in addition to the use of a distributed equalizer topology. Multistage amplifiers having a net gain of over 25 dB and a power output in excess of 0.4 W over a bandwidth of 4 GHz in X- band have been realized.

Ambient-temperature effects in transferred-electron amplifiers

The effect of ambient temperature on the gain and centre frequency of transferred-electron reflection amplifiers is reported for devices with n+ or metal-alloy cathode contacts. The dependence of the centre frequency on temperature was much stronger than predicted theoretically, and, contrary to expectation, similar performance was obtained from both types of diode.

35-GHz transferred electron amplifiers

GaAs transferred electron amplifiers with 110-mW saturated power output at 35 GHz have been designed and fabricated. Small signal gain of 13 dB, 3-GHz bandwidth, and noise figures as low as 16.2 dB have been observed. Two basic amplifier designs which have been investigated are described.

Computer simulations of the large signal characteristics of supercritical GaAs transferred electron amplifiers

The large signal characteristics of supercritically doped n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> -n-n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> GaAs transferred electron amplifiers are investigated in computer simulations. Device admittance, reflection gain in a 50-Ω circuit, available net output power, and efficiency are presented as a function of mean-square voltage across the device. Good agreement with published experimental amplifier results [1] is demonstrated.

Low-noise wideband indium-phosphide transferred-electron amplifiers

X band pulsed, InP transferred-electron reflection amplifiers have been characterised by a study of the small-signal admittance, the large-signal dynamic conductance and the noise figure. These measurements have been made as functions of voltage, frequency and temperature on a number of different vapour epitaxial layers. The lowest observed noise figure was 8.8 dB at 10.0 GHz. An instantaneous bandwidth of more than 4 GHz at 7 dB gain has been obtained using a simple impedance-equalisation circuit.

Gain and noise figure of GaAs transferred-electron amplifiers at 34 GHz

Experimental results obtained from supercritical c.w. GaAs transferred-electron reflection amplifiers at about 34 GHz are reported. Gains in excess of 20 dB have been observed with typical (gain)?×bandwidth products of 1.0?1.5GHz. The best noise figure is 18 dB, and this parameter is shown to be sensitive to the doping profile. The output power for 1 dB gain compression is typically 2.5?3.0 mW.