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NISHIZAWA Perfect Crystal
Research Director: Dr. Jun-ichi Nishizawa
(Professor Research Institute of Electrical Communication, Tohoku University)
Research Term 1981-1986
Project Description
 This project worked toward developing a new generation of semiconductors by combining silicon and gallium arsenic perfect-crystal formation and static-induction control technologies. Static induction transistors (SIT) and thyristors were developed featuring such characteristics as high operating speeds, low noise, low power consumption and large-power handling capacities. Furthermore, crystal photoepitaxy by optical irradiation has been developed as a technology which permits the control of crystal growth with minimal energy, while providing valuable data regarding crystal growth.

Research Results

Photo-excited molecular layer epitaxial growth: The growth of epitaxial films which are necessary for making GaAs compounds semiconducting elements has been realized by low-temperature (350 ), and high-precision (2.5) crystal control. This method is applicable for making ultra-high-speed switching circuits and new light-emitting elements. In terms of crystallography, new experimental facts have been obtained regarding the control and elucidation of the stoichiometric structures of GaAs single crystals.

GaAs single crystal: By introducing an arsenic pressure-control method, single crystals having very few lattice defects could be realized. This enables the manufacturing of ultra-high-speed switching elements that are two to three orders faster than ordinary silicon single-crystal elements as well as high-efficiency photo-electric transfer elements.

Electrostatic-induction type photo-sensor: Development of an electrostatic induction transistor which can amplify weak light and convert it to an electric signal. This low-power, low-noise element can detect very weak light (4x10-6 lux-sec). Super high-performance SITs are produced so thin that disturbances caused by lattice vibrations are virtually insignificant.

Double-gate type thyristor: A basic technique for manufacturing large-power, double-gate, static-induction thyristors has been established. This thyristor has a peak voltage of 1kV, a current capacity of 100 amps and a sub-microsecond switching speed. It enables the miniaturization of electric motors through the use of higher-frequency power supplies.

Ultra high-density SIT integrated circuit: An integrated circuit having a special structure and using a silicone substrate close to a perfect crystal has been manufactured. This IC enables low-power consumption ( less than 10-12 joule), ultra-high-speed switching (less than 10-9 sec) and ultra-low capacity (less than 2x10-12W). This performance is one order higher than conventional circuits.


·The top view of 64x64 bits static transistor image sensor with newly developed hexagonal pixcell structure.


·Schematic illustration of the growth mechanism of the GaAs molecular layer epitaxy.


·(a) GaAs single crystal grown by the newly developed As pressure controlled Czochralski method. (mirror-like surface)


·(b) Conventional GaAs crystal

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