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A pseudomorphic InAlAs/In0.8Ga0.2As/InP heterostructure, with the very high electron mobility of over 1.5 m2/V at room temperature, is successfully grown on InP by our molecular beam epitaxial growth system. This is the ultimate and the most promising substrate for the high electron mobility transistors (HEMT), and the high speed logic circuits as well. An ideal 1/f characteristics was observed in this material throughout the temperature range between 300 and 50 K for the electric field between 1 and 200 V/cm. The Hooge noise parameter αH of a bridge type Hall element was of the order of 10−4 at room temperature, increasing with decreasing the temperature. The parameter αH increased with the electric field at room temperature, and was independent of the electric field at 77 K

Experiments were carried out for the n-channel devices, processed in a 0.3 µm spacer less complementary metal–oxide–semiconductor technology. Random-telegraph-signal measurements were performed for the constant gate voltage. It is supposed that electron concentration in the channel decreases from the source to the drain contact. Lateral component of the electric field is inhomogeneous in the channel and it has a minimum value near the source and reaching the maximum value near the drain electrode. Drain current is given by two components – diffusion and drift ones. Diffusion current component is independent on the x-coordinate and it is equal to the drift current component for the low electric field. The model explaining the experimentally observed capture time constant dependence on the lateral electric field and the trap position is given. From the dependence of the capture time constant τc on the drain current could be calculated longitudinal coordinate of the trap position.

Current collapse has been studied in unpassivated and SiN-passivated AlGaN/GaN heterostructure devices grown on a sapphire substrate by means of low-frequency-noise measurement at low temperatures, indicating this to be the most sensitive and powerful tool for assigning the deep levels in these complex and complicated structures. Generation–recombination (G–R) noise was explicitly observed in the unpassivated AlGaN/GaN heterostructure at low temperatures (T = 50–110 K) with the activation energy of 47 meV. This level was found to be dramatically decreased by the SiN passivation, from −205 dBA Hz−1/2 down to −217 dBA Hz−1/2, the current collapse being cured at the same time. With the SiN passivation a further G–R noise corresponding to the deeper traps of 131 and 235 meV became comparable to that corresponding to 47 meV.

Some serious accidents caused by declines in arousal level, such as traffic accidents and mechanical control mistakes, have become issues of social concern. The physiological index obtained by human body measurement is expected to offer a leading tool for evaluating arousal level as an objective indicator. In this study, declines in temporal arousal levels were evaluated by nasal skin temperature. As arousal level declines, sympathetic nervous activity is decreased and blood flow in peripheral vessels is increased. Since peripheral vessels exist just under the skin on the fingers and nose, the psychophysiological state can be judged from the displacement of skin temperature caused by changing blood flow volume. Declining arousal level is expected to be observable as a temperature rise in peripheral parts of the body. The objective of this experiment was to obtain assessment criteria for judging declines in arousal level by nasal skin temperature using the alpha attenuation coefficient (AAC) of electroencephalography (EEG) as a reference benchmark. Furthermore, a psychophysical index of sleepiness was also measured using a visual analogue scale (VAS). Correlations between nasal skin temperature index and EEG index were analyzed. AAC and maximum displacement of nasal skin temperature displayed a clear negative correlation, with a correlation coefficient of −0.55.

A 250 MHz Li2B4O7 surface acoustic wave (SAW) filter was successfully designed using a newly developed program for double-mode SAW (DMS) filters. The elastic, piezoelectric and dielectric constants of Li2B4O7 grown by the resistance-furnace heating Czochralski method were measured precisely to determine the accurete phase velocity and the electromechanical coupling coefficient of SAW. The mode coupling coefficients were determined as a function of the electrode thickness as well. These coefficients were introduced in the simulation program, and the SAW filter was designed. The DMS filter fabricated in this study had almost the same characteristics as those expected from the design.

Photoluminescence (PL) analysis on n-In0.52Al0.48As/In0.8Ga0.2As/In0.52Al0.48As/InP pseudomorphic heterostructures grown by molecular beam epitaxy has been carried out to investigate the critical layer thickness. Crystal quality degradation is followed by the relaxation of the lattice-mismatched layer. The critical layer thickness for this material system that is measured by PL is found to agree with the value from the energy balance model.

Voltage noise spectrum densities of quarter-micron filaments made by GaAs, InP and heterostructures are measured in detail as a function of decreasing temperature to 10 K, and the Hooge noise parameter αH of each device is precisely determined at each temperature. Focused ion beam (FIB) implanted n-GaAs has the smallest αH of 1.0×10-8 at 60 K, decreasing from 2×10-6 at room temperature. The derived value of αH is the smallest one ever reported for compound semiconductor devices, and compares favorably with that expected from quantum 1/f noise theory. FIB-implanted n-InP has the smallest αH of about 1×10-7 at 50 K. The αH of a molecular beam epitaxially (MBE) grown In0.8Ga0.2As heterostructure depends on µpo between 1 to 10 m2/V·s, realizing 1/f noise in the cross section of optical phonon scattering.

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.

An experimental and theoretical investigation is made into the helical instability in injected semiconductor plasmas. Dispersion relations and spatial growths of the instability are studied theoretically as a function of magnetic field, injection level, and electric field. Experiments are made by launching the waves (2–30 MHz) on injected plasmas of p‐InSb with sample currents and magnetic fields in the ranges 30–150 mA and 200–1000 G, respectively. The phase shift and amplitude of the waves along the potential probes of a sample make it possible to determine the wave number, the wavelength, the phase velocity, and the spatial growth rate, and are compared in reasonable agreement with the theory. Feedback control of the launched waves as well as the spontaneous oscillations are studied, while the waves and the oscillations are compared with respect to the threshold conditions and the oscillation frequency.

Low-frequency noise in AlGaAs/GaAs single-heterostructure is studied systematically for various contact metals and device dimensions. The low frequency noise spectra varies at a rate of ƒ −1 in the devices with SnAu contacts, and a rate of ƒ −1.5 in those with AuGe contacts. Contact resistances have no effect on the ƒ −1 noise levels, but change the generation-recombination ( G − R ) noise levels induced by the trap level at 0.23 eV. A large G − R noise bulge by the trap level at 0.8 eV is observed in the AuGe contact devices, but not in those with the SnAu contacts. The noise levels of the SnAu contact device are about 22 dB lower than thoe of the AuGe contact device around 1 Hz.

Since the two-dimensinoal electron gas in the modulation-doped A1GaAs/GaAs heterojunction is as thin as 10 nm and the electron mobility is over 7000 cm2/Vs, this structure is suitable for highly sensitive Hall devices. As the room temperature device the following conditions must be satisfied: the carriers should be supplied sufficiently to the two-dimensional gas, but no excess carriers should exist in the highly doped A1GaAs layer. Thus the number of the two-dimensional electron gas should have little dependence on the temperature. The fabrication conditions of the heterojunction and the magnetic property of the devices are discussed. The product sensitivity and the figure of merit of the heterojunction Hall device were 1000 V/AT and 27 (V/A)1/2/T, respectively. These values are comparable to those of InSb Hall devices. The temperature dependence of our device was three times less than that of the InSb Hall device.

Low-frequency noise in n-GaAs layers grown by molecular beam epitaxy has been systematically studied for various carrier concentrations and device dimensions. The noise decreases linearly with an increase in total carriers and layer thickness. The frequency dependence of the noise varies at a rate of ƒ −1.5 in the devices with SnAu contacts, and at the rates of ƒ −1.2 to ƒ −2.0 in those with AuGe contacts. SnAu ohmic contacts have noise levels 20 dB lower than those of AuGe contacts. Surface cap layers either doped to n- or p-type have little effect on the overall frequency dependence of the noise.

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.

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.

A quarter‐micron‐width Greek‐cross Hall device was fabricated by focused ion‐beam implantation with a practical product sensitivity of 85 V/AT. The Hooge’s noise parameter αH [Phys. Lett. A 29, 139 (1969)] was evaluated from the exact carrier number and the 1/f noise level to be 4.5×10−6, in good agreement with the quantum theory for 1/f noise.

The frequency dependence of noise levels in ion-implanted devices of InP follows Hooge's relationship [ Phys. Lett. A-29 , 139 (1969)]. The noise levels vary in proportion to the square of the terminal voltages, and decrease linearly with the frequency and the total carriers throughout the ranges from 0.1 Hz to 100 kHz. The Hooge parameter is α H = 1.5 × 10 −4 .

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.

Photoluminescence measurements of Be-doped GaAs, grown by molecular beam epitaxy, were carried out at low temperature as a function of acceptor concentration. Results revealed that besides the well-defined emission, [g-g], which is exclusively relevant to acceptor impurities, an additional specific emission, temporarily denoted by [g-g]α is formed near the band-edge, when the concentration of acceptors exceeds 1×1019 cm−3:. From the viewpoint of application it was suggested that also in case of acceptors, photoluminescence spectra can be practically used for the precise determina-tion the acceptor concentration.

Electrical properties of heavily Be-doped GaAs grown by molecular beam epitaxy were investigated systematically in a wide range of Be-concentration from 1× 1014 up to 2× 1020 cm-3 by using yan der Pauw technique. Probable carrier scattering mechanisms observed in this work are discussed by taking into account the radiative mechanisms of several new photoluminescence emissions previously observed in the band-edge-emission region of the samples. All samples were checked their electrical properties first at room-temperature. Five selected samples out of them were measured from 10° K up to room-temperature. Samples having the carrier concentration from 1014 to 1018 cm3 presented typical semiconductor-like conduction with finite carrier excitation energy. For samples having carrier concentration 7× 1016 cm -3, the conduction mechanism at high temperature region above 30β K was dominated by holes thermally excited into valence band. At low temperature region below 30° K . it was dominated by holes hopping from neutral to ionized acceptors with the assistance of phonons. Hole mobilities of samples having the carrier concentration from 1017 to 1018 cm-3 showed an anomalous behavior in the low temperature region, which suggests the presence of a new type of carrier scattering mechanism. A radiative center denoted by lg-gl observed in this concentration region will be a candidate scattering center to explain these electrical behaviors. Samples having the carrier concentration larger than 1019 cm-3 demonstrated typically metallic electric conduction not owing to thermally excited carriers, which means that an impurity band is formed but merged with valence band. The density of state of this combined valence band mixed with impurity band can be supposed to reflect carrier concentration dependence of the PL emission bands observed in this region, i.e. [g-g]α , [g-g]β and [g-g]γ .

Fabrication processes to make an excellent p + n-junction on bulk n-InP by 24Mg-ion implantation are described. The leakage-current density through a junction was less than 10-7 A/cm2 with a rectification ratio larger than 106 at a bias voltage of - 1 V and a junction breakdown voltage below - 60 V without any guardring structure. A 2.0-mm long junction waveguide was used to control the long-wavelength (λ=1.135 µm) light with an extinction of 8.6 dB at 10 V.

A self-aligned-gate inversion-mode InP metal-insulator-semiconductor field-effect transistor (MISFET) was successfully fabricated by using plasma-assisted chemical-vapor-deposited Si3N4 film both as the insulator and as the capping layer for the annealing process. A channel mobility of 2700 cm2/Vs and a transconductance of 55 mS/mm at a gate voltage of 4 V were achieved with a reasonably low source-drain leakage current.