The tunnel diode originated in 1957 when Leo Esaki discovered that thinning the p–n junction of germanium allowed for electron tunneling, a phenomenon that demonstrated solid-state quantum effects. This work, conducted during his tenure at Sony, provided the foundation for modern quantum electronic devices and earned him a share of the 1973 Nobel Prize in Physics.
Academic and Early Career
Born in Takaida, Japan, on March 12, 1925, Esaki pursued his scientific education at the Third Higher School before attending the University of Tokyo, where he earned a B.S. in 1947 and a Ph.D. in 1959. Following his undergraduate studies, he joined Kobe Kogyo Corporation. By 1956, he had transitioned to Tokyo Tsushin Kogyo, the company now known as Sony, where he served as chief physicist and conducted his seminal research on semiconductor tunneling.
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In 1960, Esaki moved to the United States to join the IBM Thomas J. Watson Research Center, receiving an appointment as an IBM Fellow in 1967. During this period, he expanded his research into semiconductor superlattices. By 1969, he predicted that these structures could induce negative-resistance effects through periodic variations in crystals. He developed the molecular-beam epitaxy method for crystal growth in ultrahigh vacuum to realize these structures, successfully achieving his concept in III-V group semiconductors by 1972.
Institutional Leadership and Later Recognition
Returning to Japan in 1992, Esaki held administrative roles including the presidency of the University of Tsukuba, a position he maintained until 1998. Throughout his career, he has held academic and research positions at institutions including Kwansei Gakuin University, the Shibaura Institute of Technology, and the Yokohama College of Pharmacy. In 2015, his contributions were honored with a bronze statue in Tsukuba’s Central Park, standing alongside fellow Nobel laureates Shin'ichirō Tomonaga and Makoto Kobayashi.
Fast facts
- Born: 12 March 1925, Takaida, Japan
- Nobel Prize in Physics: 1973
- Ph.D.: University of Tokyo, 1959
- IBM Fellow: Appointed 1967
- Japan Academy Prize: 1965
- Fellow of the American Physical Society: 1960
- Oldest living Japanese Nobel laureate as of 2015
Questions readers ask
What is the Esaki diode?
It is a quantum electronic device based on the tunnel effect in semiconductors, which exhibits negative resistance as voltage increases.
What are Esaki's five don'ts?
A set of guidelines for creative potential that includes avoiding entrapment by past experiences and maintaining childhood curiosity.
