SCHOTTKY, WALTER

born July 23, 1886, Zrich, Switz. died March 4, 1976, Pretzfeld, W.Ger. German physicist whose research in solid-state physics and electronics yielded many devices that now bear his name. Schottky obtained doctorates in engineering, technology, and natural sciences from the University of Berlin, where he conducted research under Max Planck. He taught at the universities of Wrzburg (192022) and Rostock (192327) and then worked as an industrial researcher at Siemens AG from 1927 until shortly before his death at age 90. In 1914 Schottky discovered an irregularity in the emission of thermions in a vacuum tube, now known as the Schottky effect. He invented the screen-grid tube in 1915, and in 1919 he invented the tetrode, the first multigrid vacuum tube. In his book Thermodynamik (1929), he was one of the first to point out the existence of electron holes in the valence-band structure of semiconductors. In 1935 he noticed that a vacancy in a crystal lattice results when an ion from that site is displaced to the crystal's surface, a type of lattice vacancy now known as the Schottky defect. In 1938 he created a theory that explained the rectifying behaviour of a metal-semiconductor contact as dependent on a barrier layer at the surface of contact between the two materials. The metal semiconductor diodes later built on the basis of this theory are called Schottky barrier diodes.