Transferred Electron Oscillators Research Articles

Transferred-electron oscillations in In0.53Ga0.47As

Transferred-electron oscillations were observed and investigated in planar devices of In0.53Ga0.47As. The peak-to-peak magnitude of oscillations with respect to the device current at threshold field was as high as 70%, indicating the peak-to-valley velocity ratio of 3.3:1 for this material. The domain velocity was estimated from the oscillation frequency (2 GHz) and the corresponding device length (40 µm) to be 8×106 cms¯1. The results presented in the letter show a promising prospect for TED applications of this ternary alloy.

Indium phosphide vapor phase epitaxy: A review

This paper describes the vapor epitaxy of indium phosphide using the phosphorus trichloride chloride system. In the dynamic equilibrium between the gaseous reactants (PCl 3, H 2, HCl, P 4), a solid (InP) and a liquid (In-InP solution), three factors are known to influence the growth rate and impurity incorporation rate during epitaxial deposition: (1) the phosphorus trichloride mole fraction; (2) the indium to phosphorus ration over the seeds; (3) the temperature gradient across the indium-indium phosphide source metal. These system constraints are interrelated and prove difficult to optimize; nevertheless, unintentionally doped layers of InP with residual doping levels below 1 x 10 13 cm -3 have been produced along with superimposed submicron doping profiles for Transferred Electron Oscillators (TeOs) and Field Effect Transistors (FETs). TEO layers with controlled carrier concentration profiles containing narrow highly doped layers less than 300 Å thick have been fabricated using advanced doping techniques. Recent work on FET structures has provided semi-insulating buffer layers on iron doped InP substrates with sulfur doped, 0.5–0.3 μm thick surface channel layers which have demonstrated an electron mobility of 3800 cm 2/V·s at 1 x 10 17 cm -3 carrier concentration at 298 K. A discussion of the vapor phase reactor design, the reaction mechanism and crystal morphology is given and a modified method for indium phosphide epitaxy is discussed.

Efficient fundamental frequency oscillation from millimetre-wave indium phosphide n+-n-n+ transferred electron oscillators

The letter describes the development of CW indium phosphide, transferred-electron oscillators (TEOs) with emphasis being place on the achievement of efficient operation in the millimetre-wave frequency range. Reasons are given for the choice of the n+-n-n+ epitaxial structure used, together with relevant material growth and characterisation details. A brief outline of the device fabrication technology is given before discussing oscillator performances. Results are presented for operating frequencies from 30 to 110 GHz which show that the three-layer indium phosphide device is capable of much higher conversion efficiencies than the equivalent gallium arsenide structure at frequencies above 40 GHz. From these figures it is concluded that indium phosphide will supplant gallium arsenide as a mm-wave TEO material.

Transferred-electron oscillators at very high frequencies

The high-frequency characteristics of transferred-electron oscillators have been examined by computer simulation. Maximum frequencies in the range 100 to 200 GHz (for GaAs) and contact effects favouring current saturating cathodes are predicted.

Operating modes of millimetre wave transferred electron oscillators

The harmonic content of both GaAs and InP millimetre wave transferred electron oscillators has been measured using a Michelson interferometer. The operating modes of these devices as a function of active length and frequency have thus been identified. Additionally, the higher frequency capabilities of InP as a millimetre wave oscillator material have been demonstrated.

Harmonic operation of GaAs millimetre wave transferred electron oscillators

Harmonic operation of GaAs millimetre wave transferred electron (TE) oscillators has been identified using a wideband waveguide system. The harmonic number was determined by precisely measuring the frequency as well as the frequency variations of the harmonic components when the oscillator was tuned mechanically or electrically. We find that GaAs TE oscillators at 94 GHz, matched to a waveguide circuit by means of a resonant disc, operate at the second or third harmonic frequency, depending on the length of the active GaAs region, which was between 1.8 and 2.6 ?m.

Noise reduction in transferred electron oscillator modules

The FM noise performance of oscillator modules based on GaAs transferred electron devices characterized by carrier notches close to the cathode contact is presented. The notches have been incorporated into completed and encapsulated devices by ion-implantation techniques, the notches proving stable up to 400°C. Useful improvements in the FM noise performance close to the carrier are available using this technique.

Stabilization of a solid-state microwave oscillator by cavity coupling

A transferred electron oscillator (TEO) is a non-linear device. Its operation depends on the circuit loading at the fundamental and harmonic frequencies. This paper discusses a method of stabilization of a TEO by coupling an auxiliary cavity to the oscillator and adjusting the same for optimum performance. Added advantages are noise reduction and finer tuning capability. Experimental results and computer analysis are also discussed.

Large-signal computer simulations of the contact, circuit, and bias dependence of X-band transferred electron oscillators

We present a treatment synthesizing the roles of the contact and the circuit for X -band length transferred electron devices sustaining self-excited oscillations. The contact is modeled with specific cathode electric-field relations. The circuit is modeled with lumped elements. The scope of the simulation is relevant to both high-efficiency InP oscillations and the moderate-efficiency GaAs oscillations.

A versatile solid-state mic source module for Ku-band

A phase-locked-loop approach has been adopted in order to realize a Ku-band transferred electron source with good power, stability and operational bandwidth. By arranging to interface with a u.h.f. reference, namely one of the new generation surface acoustic wave oscillators, the multiplier is simplified and the whole of the microwave circuit can be configured on a single compact m.i.c. The problem of maximizing the output of the transferred electron oscillator source in the rigid stripline medium has been solved by providing manual tuning elements together with an edge mounted device. Details of the circuit design and operation of the module are given.

A New Look at Noise in Transferred Electron Oscillators

Low-frequency current and voltage fluctuations have been measured, and it has been confirmed that noise in packaged transferred electron devices (TED's) is due to three distinct noise mechanisms: flicker, generation-recombination, antd thermal noise. For transferred electron oscillators (TEO's), this low-frequency noise is upconverted into the microwave frequency range and adds to the intrinsic RF noise. We have found that between 1 kHz and 1 MHz off the carrier, temperature-dependent generation-recombination noise is the main contributor to the total noise. A model of a noisy TEO is presented. This model permits the calculation of AM and FM noise spectra from device and circuit parameters for measured low-frequency noise or the derivation of device characteristics from noise and circuit parameter measurements.

Photoetching of InP mesas for production of mm-wave transferred-electron oscillators

A novel technique for fabricating small-diameter mesa-shaped structures on semiconducting substrates is described. The mesas, which are formed by etching and selective illumination of the substrate, show very little undercutting. The technique is suited for fabricating InP and GaAs transferred-electron oscillators, as well as impatt-diode structures for millimetre-wave sources.

Second-harmonic locking properties of l.s.a.-mode transferred-electron oscillators

Harmonic injection locking of an l.s.a.-mode oscillator has been studied by computer simulation. The results show that under certain circuit conditions the 2nd-harmonic frequency locking range may exceed that of the fundamemtal.

High-efficiency and high-peak-power InP transferred-electron oscillators

It has been demonstrated that a current-limiting cathode contact can be used to improve the performance of relatively thick vapour eptaxial InP transferred-electron devices. A peak power of 120 W with 18% efficiency at 5 GHz has been obtained from 34 μm-thick active-layer devices with silver tin-alloy metal contacts.

Measurements of the close-to-carrier f.m. noise of pulsed InP t.e.o.s primed by an external oscillator

Experiments on phase-primed, pulsed InP transferred-electron oscillators show that the noise due to priming jitter can be reduced below the inherent noise level of the oscillator. Measurements are presented on the magnitude and spectrum of the oscillator noise.

Dynamic cathode boundary fields and transferred electron oscillators

The evolution of a generalized time-dependent cathode boundary field model is discussed, and calculations are presented which demonstrate its applicability for explaining such diverse phenomena as 1) the appearance of anomalously high efficiency oscillations in InP and 2) the more moderate oscillatory behavior associated with GaAs.

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.

High efficiency CW transferred-electron oscillator with optimized doping profile

This study is aimed at helping to design X-band CW transferred-electron oscillators with higher performance. Temperature rise in devices operating in the accumulation layer mode is analyzed both with heat sink negative and heat sink positive. Efficiencies and output powers in both polarities are calculated and compared. The calculation shows efficiency in CW operation is drastically improved by quantitatively controlling the doping profile to account for the temperature profile and further governed by carrier concentration times layer thickness (n × l) product and diode size. For the heat sink negative, output power over 800 mW is predicted from a single-mesa conventional structure, using a wafer with an n × l product of 2.0 × 1012cm-2and doping profile increasing, toward the substrate (away from the heat sink), by 30-35 percent across the active layer. For the heat sink positive, an almost flat profile is suitable and output power over 1.5 W is predicted for a diode with a doping increase of 10 percent across the active layer toward the substrate. The calculations are substantiated experimentally by diodes with n × l products of 1.5-2.3 × 1012cm-2and doping increases of 20-70 percent across the active layer toward the substrate heat sink negative operation.

K-band Transferred Electron Oscillator

Transferred electron oscillator developed in K-band (18–26.5 GHz) is reported. Frequency and power characteristics of the oscillator are presented. It is observed that a mechanical frequency tunability of nearly 5 GHz with a minimum output power of 10 mW is obtained.

Doppler Radar Microwave Source Design for Automotive Braking Applications

ABSTRACTThe problem of wheel and road speed measurements in automotive anti-skid systems is discussed and a microwave doppler radar solution proposed. A simple optimisation procedure for the transferred electron oscillator using a self-mixing detector is described, based on a new current waveform approximation and equivalent circuits for the device and oscillator structure, and allowing direct observation of the effects of device and circuit parameter changes on the overall performance of the detector. The operation of transferred electron and Barritt devices is compared with reference to sensitivity and signal to noise ratio, and reliability under the strict environmental conditions imposed by the application. A hybrid integrated circuit containing both microwave and signal processing circuitry is described.