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Japanese physicist Leo Esaki won the 1973 Nobel Prize in physics. He proved the concept of tunneling in semiconductors and developed the tunnel diode.
Leo Esaki, born in 1925, Japanese physicist whose groundbreaking work on semiconductors earned him a Nobel Prize in 1973. Esaki proved the concept of tunneling in semiconductors and developed the tunnel diode, also known as the Esaki diode. In classical physics, an electric current cannot flow in a circuit interrupted by an insulating barrier—that is, when electrons reach the “wall” of insulating material, they cannot continue forward. Since the 1930s, quantum mechanics, the branch of physics that studies the motion of subatomic particles and related phenomena, had predicted that electrons might be able to “tunnel” through an insulating barrier if it were thin enough. Esaki developed a diode with electrical junctions only 10 billionths of a meter thick through which electrons could tunnel. Esaki shared the Nobel Prize with Norwegian-born American physicist Ivar Giaever and American physicist Brian D. Josephson.

Esaki was born in Osaka, Japan. He attended the University of Tokyo, where he earned a B.S. degree (1946), an M.S. degree (1947), and a Ph.D. degree (1959) in physics. While studying for his doctorate, he worked in Tokyo at Kobe Kogyo Corporation and Sony Corporation. His discovery of tunneling occurred at Sony in 1957 while he was still a student. Esaki moved to the United States in 1960 to join the Thomas J. Watson Research Center at IBM in New York. His research focused on semiconductor physics. He was made an IBM fellow, the company's highest research position, in 1965. He began work in superlattices as part of an effort to demonstrate other predicted but unproven theories of quantum mechanics. Superlattices are synthetic crystals composed of extremely fine layers of different semiconductors. One of the potential uses for this material is in high-speed computers. Esaki stayed at IBM for 33 years, eventually becoming a director of the company. During this period, he also lectured at the University of Pennsylvania and the University of Tokyo. When he retired from IBM in 1993, Esaki returned to Japan. Since then he has served as president of Tsukuba University.