• Dr. Leo Esaki


    Biography
    1947 Graduated from Department of Physics, Faculty of Science, University of Tokyo
    1947 Entered Kobe Industry Co., Ltd.
    1956 Entered Tokyo Telecommunication Co., Ltd. (Currently SONY Corporation)
    1959 Received PhD in Science from the University of Tokyo
    1960 Engaged in semiconductor research at the IBM T. J. Watson Research Institute
    1975 Became a member of the Japan Academy
    1992-1998 President of the University of Tsukuba
    1998- Chairman of the Science and Technology Promotion Foundation of Ibaraki
    2000-2005 President of the Shibaura Institute of Technology
    2006- President of Yokohama College of Pharmacy


    Award

    1959 Nishina Memorial Prize
    1960 Asahi Press Award and Toyo Rayon Foundation Award for the Promotion of Science and Technology
    1961 Morris N. Liebmann Memorial Prize from IRE, and the Stuart Ballantine Medal from the Franklin Institute
    1965 Japan Academy Prize
    1973 Nobel Prize in Physics
    1974 Order of Culture
    1985 American Physical Society 1985 International Prize
    1991 IEEE Medal of Honor
    1998 Japan Prize

    Research Works

    The works of Dr. Esaki are broad-ranging. In particular, the following two works should be cited as very significant findings in the field of semi-conductor physics which underpin the basis of current electronics. These works are very innovative ones which opened a new field greatly influencing the whole of condensed matter physics.

    1) Discovery of the tunneling effect at PN junctions of semi-conductors

    In the late 1950's, Dr. Esaki discovered a characteristic called negative resistance whereby, for PN junction diodes with a large amount of impurities added, the current decreases with increasing voltage, and confirmed that this phenomenon is due to the quantum mechanical tunneling effect of electrons.
    By this experimental finding of the tunneling phenomenon in solids, a new field of solid-state electronics called tunneling spectroscopy was created, and moreover electronic devices called Esaki-diodes were developed. Tunneling spectroscopy has dramatically evolved into the study of tunneling phenomena in metals and superconductors. For this great contribution, he was awarded the Nobel Prize in physics together with Dr. B. D. Josephson and Dr. I. Giaever in 1973.

    2) Proposal and realization of the concept of semi-conductor superlattice

    In 1969, Dr. Esaki predicted that if one-dimensional periodic structural changes are artificially built in semiconductor crystals, semiconductor superlattices will be formed to induce unique phenomena such as a differential negative-resistance effect. He developed a thin-film crystal growth method, which can be regulated quite precisely in ultrahigh vacuum, called molecular beam epitaxy. In 1972, he realized superconductor artificial superlattices in III-V group semiconductors, leading to the finding of negative resistance characteristics predicted.
    He also found resonant tunneling phenomenon induced between neighboring potential wells. His concept of artificial superlattices was later extended to a wide range of fields from semiconductors to metals and magnetic materials, and is still evolving to inspire new studies and to discover unknown characteristics, leading to applications serving human needs. For these contributions, Dr. Esaki was awarded the Japan Prize in 1998.

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