Nobuo Hashizume

Performance and principle of operation of GaAs ballistic FET

This paper reports the first successful Monte Carlo particle simulation of submicron GaAs FETs of practical interest. The unsubstrated FET of a self-alignment type,<tex>N_{d}=7 \times 10^{16}</tex>cm^-3,<tex>L_{g}=0.25</tex>µm, and the channel thickness of 0.1µm shows<tex>I_{ds}, g_{m}</tex>, and<tex>f_{T}(=g_{m}/2</tex>πC<inf>g</inf>) of 3.3mA/20µm, 600mS/mm, and 160GHz, respectively. The FiT shows virtually no difference in the performances between 77K and 300K operations. Principle of operation of this high-performance FET has been made clear. The results on submicron GaAs FETs having 1) an undoped GaAs substrate 2) a hot-electron-injecting source structure, 3) a Permeable Base Transistor type structure, and 4) different doping densities are also reported.

Anisotropy and Hysteresis Behavior of Galvanomagnetic Effect in Super Magneto-Resistor

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.

Gunn effect high-speed carry finding device for 8-bit binary adder

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.

Improvement in sensitivity of novel magnetic sensor using Y-Ba-Cu-O ceramic superconductor film

The authors report an improvement in the sensitivity of a magnetic sensor made of high-T/sub c/ ceramic superconductor. The sensitivity is discussed in connection with the noise measurement of a film element. It is believed that a high sensitivity comparable to that of a high-T/sub c/ SQUID (superconducting quantum interference device) utilizing ceramic materials can be obtained with the present magnetoresistive superconductive element. The magnetic field dependence of the electric resistance of the element at 77 K is shown. The sensitivity as a function of the current is compared for various elements. It is found that the sensitivity of this element is about 100000 times higher than that of a bulk element reported last year. The magnetoresistance at low magnetic field is attributed to the weak couplings between superconductive grains in a ceramic semiconductor. Thus the ceramic superconductor is considered to be a multiconnected Josephson network. The noise is mainly due to the presence of trapped magnetic flux. The reduction of the noise for parallel magnetic field implies the elimination of the trapped flux. Noise measurements are also reported.<<ETX>>