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Magnetic field dependence of voltage noise in a ceramic superconductor Y1Ba2Cu3O7-x film has been investigated. We have observed a maximum of the noise at about 10 Oe for the perpendicular field to the film surface. For the parallel field to the film surface, the noise increases slightly with the increase of the field. These noise characteristics are considered due to a motion of magnetic flux in the film.

The stability of a linearly pinched cylindrical plasma is investigated in the absence of an external magnetic field. The theory is based on the magnetohydrodynamic equations of motion and the particle conservation combined with Maxwell's equations. The dispersion relation of the instability and the explicit dependence of the wave parameters on the field are obtained by linearizing the equations for axially symmetrical harmonic perturbation. Numerical results on the threshold show that the axial current required to cause the instability is inversely proportional to the electric field, and that the oscillation frequency increases linearly with the electric field while the wave number remains approximately constant. The spatial growth rate and the phase velocity of the instability are also obtained as a function of the field strength.

An Experimental investigation is made on the sausage-shaped instability in an impact ionized plasma of n-InSb. Sinusoidal voltage oscillations are observed after complete confinement of a pinch without an external magnetic field, and the frequency is measured as a function of a sample current. Oscillation frequencies and currents at a threshold are obtained as a function of an applied electric field and compared with the dispersion relation theoretically obtained. Theoretical considerations are in good agreement with the experimental results on axial magnetic field stabilization of the oscillations.

High field domain characteristics in n-GaxIn1-xSb (0.4≤x≤0.82) were investigated by current-voltage and potential probing measurements. Domain velocity varies from 1×107 cm/s for x=0.4 to 0.5×107 cm/s for x=0.82 but remains constant irrespective of the applied voltage or the presence of avalanche breakdown in the domain. Domain formation time is estimated to be less than 70 ps for x=0.82, n=6×1015 cm-3 and l=400 µm long diode.

The light beam from a GaAs injection laser (9050 A) was modulated at 0.1 GHz by the Pockels effect of a traveling high−field domain in a GaAs Gunn diode at room temperature. The Gunn diode is 80 μm thick, 600 μm wide, and 1 mm long, and has carrier concentration of 6.3×1013 cm−3. The laser beam was focused on the center of the wider surface of the Gunn diode through a lens and a polarizer and the transmitted light was detected with a Si photodiode through an analyzer in a cross arrangement. It was found that the detected output was modulated with a S/N ratio better than 10. The Franz−Keldysh effect of the high−field domain was also measured, and a quantitative correction was made to the observed Pockels effect. It is shown that the retardation is linearly proportional to the square root of the domain voltage and also that the electric field of the domain calculated by the corrected value of the Pockels effect agrees well with the one measured by a capacitance probe.

The electron velocity-field (v–E) characteristics of GaxIn1-xSb in the composition range 0.4≤x≤0.9 are measured by a microwave heating technique at 35 GHz at room temperature, to study the transferred electron effect at high frequency. New microwave cavity perturbation tequnique is developed to measure a small signal conductance against the absorbed power in order to obtain the v–E curve. The results indicate that all samples except one of x=0.4, show negative differential mobility characteristics above the threshold field. The threshold field increases from 430 V/cm to 1200 V/cm and the negative mobility decreases with increasing x. For x=0.4, an impact ionization prevents from mesuring a negative differential conductivity. These results suggest that a useful Ga composition range of x for transferred electron devices is between 0.55 and 0.82, and that the response time of hot electrons is not much different from that in GaAs.

Epitaxial growth of Gax In1-x Sb on InSb or GaSb substrate was made by using a vertical dipping-type furnace, over a whole range of x to investigate the surface morphology of the grown crystal, interface between the epitaxial layer and substrate, electrical properties and lattice constant, in connection with the type of surface, i.e. A or B, of (111) InSb substrate. The growth rate was always about 1.7 times higher on the A surface than on the B surface, irrespective of the value of x. The surface morphology of the grown epitaxial layer depends much on the type of surface of the InSb substrate, and also on the layer thickness. However, the electrical properties do not depend on the type of the surface of the substrate, and agree with the reported results. The InSb substrate was eroded to take Ga metal in it during the epitaxial growth. The reason for the erosion is explained by use of the free energy and the observed disagreements in the phase diagram are discussed in detail.

Continuous coherent oscillation from nInSb at 77°K under transverse magnetic field is investigated experimentally. The oscillation frequency is measured in detail as a function of the magnetic field together with the threshold relation between the magnetic field and the current. Interpretation is made in terms of the helical‐mode instability both on the threshold and in the growing‐wave conditions assuming the formation of a microplasma filament.

The effective magnetoresistance and Hall effects in inhomogeneous semiconductors with high carrier mobility have been calculated by using a stratified medium model. The theory shows that the effective magnetoresistance consists of two contributions, one proportional to sin 2 ϕ and the other with sharp dependence on ϕ, ϕ being the angle between the magnetic field and the current, and that the Hall effect is the same as in a homogeneous medium. The sin 2 ϕ dependence is mainly due to the physical magnetoresistance and the sharp one due to the stratified inhomogeneities in electron concentration. Experiments were made with high purity n -type InSb at 77°K under magnetic fields up to 1.5 weber/m 2 , showing a good agreement with the theory. It is concluded that the measured values of the magnetoresistance in high purity n -type InSb specimens at 77°K can be explained by considering the influence of stratified inhomogeneities in electron concentration, in addition to the physical magnetoresistance .

Adiabatic compression model for the linear pinch in avalanching n -InSb is studied experimentally. The pinching radial velocity and the final pinched radius are determined from the cross sectional dependence of the pinch time, and compared with the theory. Semiconductor plasma is heated up to a temperature just below the melting point according to the adiabatic compression in the low and intermediate sample axial current.

Theoretical calculation has been made on high-frequency transport properties of InSb under a d.c. magnetic field, leading to the conclusion that the relative increase of microwave loss in InSb under a magnetic field, γ l , is given by γ 0 {1+ω(τ e +τ h )}, where γ 0 is the relative resistivity increase Δ ρ/ρ 0 under a d.c. magnetic field with d.c. current, and τ e and τ h are the constant relaxation times for electrons and holes respectively. Measurements were made on the microwave power loss at 34 Gc/s at room temperature under magnetic fields up to 1.5 weber/m 2 . The experimental results show an appreciable influence of ωτ on the loss even at room temperature as predicted by the theory.

Detailed measurements of the oscillation frequencies in n‐InSb at 77°K as a function of dc sample current and magnetic field are described. These show the existence of two modes of instabilities, which are in the ranges of 0.2 to 0.8 GHz and of a few to several tens of MHz, respectively.

Stabilization of pinch oscillations in an avalanching n‐InSb by an axial magnetic field is experimentally studied in detail, and reasonable agreement is obtained with theoretical considerations based on a model of sausage instability in the adiabatically compressed linear pinch.

A new type of Gunn effect gate device was reported by us earlier and demonstrated in the form of a 4 bit gate device(1). The 4 bit gate device consisted of four cascaded inhibitors, each inhibitor being an integration of a Schottky electrode-triggered Gunn device and a m.e.s.f.e.t. The device had the high-speed property of the Gunn device and the stability of operation inherent to the m.e.s.f.e.t. operated in an on-off mode. This paper reports the application of such inhibitors to a high-speed carry finding device. The inhibitors have been improved in construction and operation in many ways. The most important improvement is the attachment of a memory function to the inhibitor whereby the output signal is held for any long time desired even the input signal comes in the form of a pulse of short duration. The memory makes use of the accumulation of excess electrons on the Schottky trigger electrode. Such an arrangement has also brought a remarkable improvement in the anode voltage margin.

The hysteresis behavior, fluctuation and their anisotropy of galvanomagnetic effect in novel magnetic sensor using bulk and film samples of ceramic superconductor Y-Ba-Cu-O have been measured. For the bulk element, the hysteresis was observed and its property was independent of the direction of magnetic field. For the film element, when the magnetic field direction was perpendicular to the element surface, the hysteresis was observed in a way similar to the bulk element, but when the magnetic field direction was parallel to the element surface, the hysteresis was eliminated to zero and fluctuation of output voltage was greatly reduced. These properties can be explained by considering the dynamics of magnetic flux trapping in the element.

BaTiO3 films were prepared onto InSb or GaAs semiconductor by RF sputtering with a tetrode apparatus at about 300°C. Analysis by x‐ray diffraction patterns shows that the films are of tetragonal structure of BaTiO3. Electrical properties of these films were measured and the Curie point was observed at 120–140°C.

Experimental results of efficient magnetic bubble detection with a semiconductor Hall element larger than a magnetic bubble by the full use of the magnetic flux from a bubble are described. Experimental results with InSb Hall elements of various geometries for a bubble in YFeO 3 revealed that the maximum output appeared with a Hall element slightly larger than a bubble. About 4.4 mV with an S/N of 18 dB was obtained at 23 mA with a n-type InSb Hall element of 235 × 105 × 3.5 µm3and 30 Ω for a 98-µm bubble in a 60-µm thick YFeO 3 at a bias field of 30 G and at a rotating field of 2 Hz. This arrangement may especially be useful for the detection of a small bubble in garnet, because the Hall element can be made larger, resulting in the easier fabrication and higher output.

New functional devices making use of the transverse spreading of a high-field domain in an H shaped n type GaAs sample are proposed, with some experimental results. It is expected that such devices will perform complex logic operations, such as a modification of Sheffer's stroke at extremely high speed.

Improvement was made on our recently reported Gunn-effect high-speed carry finding device, which can now perform logic operations with a minimum delay time of 20 ps/gate. The improvement is concerned with the means of nullifying the effect of the nonuniformity of the constituent m.e.s.f.e.t.s.

The galvanomagnetic effect of a ceramic superconductor Y1Ba2Cu3O7-x was measured. It was found that when a magnetic field of a certain small value applied, the electric resistance of this material suddenly increases very rapidly from zero with increases in the applied magnetic field. The magnetic field at which the resistance appears is controllable by changing the magnitude of a current through the material. This effect is characterized by a very high magnetic sensitivity at low magnetic field. This is quite useful as a highly sensitive magnetic sensor both in digital and analogue operations. This magnetic sensor using the ceramic superconductor has many advantages over the conventional semiconductor magnetoresistive sensor.

The properties of high-field domains in GaxIn1-xSb Gunn diodes (0.4 x > 0.55 and 10×106 cm/s for x = 0.4, but they are almost independent of the applied voltage, even if the electron concentration is increased by the impact ionisation in the domain at high applied voltages for the small-x samples.

A new Gunn-effect memory device using the charge accumulation on a Schottky-trigger electrode is proposed and its operation demonstrated with a monolithically fabricated device. Theoretical calculations show that the device could be modified into a static memory device if the Schottky electrode potential is chosen as the output.

The electrical resistivity, R, and its temperature derivative, dR/dT, have been measured for Y1Ba2Cu3O6+x as a function of temperature from 400°C up to 750°C. Both R and dR/dT reveal anomalous increments between about 450°C and 580°C. The increments in resistivity (excess resistivity), Δ R, and dR/dT have peaks at around 550±20°C. From the thermogravimetric measurements for the Y1Ba2Cu3O6+x samples, an anomaly was found to occur near the structural phase transition temperature. A possible origin of the anomaly is also discussed.

EPR of Cu2+ and Gd3+ in Y1Ba2Cu3O6+x have been studied between about 85K and 300K. Experiments reveal that EPR linewidths are temperature independent for both ions. This indicates that the magnetic interaction between these ions and conduction electrons is vanishingly small. Experiments also indicate that phonon instability such as softening may not occur in the YBaCuO system in the temperature range.

Electron accumulation on the metal sides of two Schottky diodes connected metal to metal was observed as a result of the temporary variation of bias between the semiconductor sides of both diodes. The potential of the metals was found to be predictable by a theory based on a property of the Schottky diode.

A high-speed carry finding device consisting of seven inhibitors, each an integrated Schottky electrode-triggered Gunn device and an m.e.s.f.e.t., was fabricated monolithically. The device could find and store carry signals of all digits in 330 ps at the worst logic case. The anode-voltage margin was 11%

It has experimentally been shown that the travelling domain oscillations in an n type GaAs bulk element can be suppressed by applying externally a large microwave-signal electric field. A computer calculation indicates a possibility of amplifying the signal when the element mounted in a stripline is subject to such a relatively large microwave signal.

Experimental results are given which show that, in a m.i.s.f.e.t. type GaAs bulk device, a negative voltage applied to the gate electrode can nucleate a high-field domain under the gate electrode, but that its subsequent departure for the anode is allowed or inhibited depending on the device structure and operating conditions.

It is shown that travelling high-field-domain-mode oscillations in GaAs, with n0l > 1012cm-2, can be suppressed by attaching a dielectric material of high permittivity (BaTiO3) to the surfaces of the GaAs. Experimental results observed with a sampling oscilloscope are given.

The transverse spreading velocity of a high-field domain, triggered by a pair of capacitive electrodes at the middle of a planar-type GaAs bulk element, was measured as a function of the bias electric field. The results show that the velocity increases from about 108 to 109 cm/s with an increase of the bias electric field from 2.8 to 3.15 kV/cm.

Computer analysis based on a 2-dimensional model was performed to investigate the effect of dielectric surface loading on the growth of dipole domains in a GaAs bulk element. The results show that a dipole domain originally produced by an inhomogeneity in GaAs is prevented from developing, as most of the space charges are concentrated near the surface boundary of GaAs by the presence of dielectric material.

Experiments were performed to investigate the effect of dielectric surface loading on GaAs bulk element. Current instabilities through the element were observed with a sampling oscilloscope while a dielectric sheet moved along a GaAs element. It was found that travelling-domain-mode current oscillations are suppressed and disappear only when the whole length of GaAs surface is covered with the dielectric sheet.

Measurements were made for a transverse spreading velocity of a high-field domain in a 3-terminal GaAs Gunn device. The result shows that the velocity is higher than 109 cm/s. This suggests that the high-field region spreads transversely with the speed of electromagnetic waves in a negative-conductivity material.