Kroemer << KROH muhr >>, Herbert (1928-2024), a German-born American physicist, won a share of the 2000 Nobel Prize in physics for his work on certain kinds of electronic devices. Kroemer shared the prize with the Russian physicist Zhores I. Alferov and the American electrical engineer Jack S. Kilby. 
Kroemer’s prizewinning work involved the use of semiconductor heterostructures in electronic devices. These structures consist of two or more thin layers of different semiconductors. A semiconductor is a material that conducts (carries) electric current better than an insulator, such as wood or glass, but not as well as a conductor, such as silver or copper. In an electronic device, all the layers of a semiconductor heterostructure act together to perform a single function, such as controlling the flow of electric current.
Commonly used heterostructure materials include gallium arsenide and aluminum gallium arsenide. However, the most commonly used semiconductor, silicon, is seldom used in heterostructures. Most computer chips contain transistors (electronic switches) that use silicon.
Heterotransistors (transistors that use semiconductor heterostructures) can operate much faster than ordinary transistors. In addition, amplifiers equipped with heterotransistors create relatively little noise. High-speed, low-noise amplifiers that employ heterotransistors have proved useful in many applications, including mobile telephones and satellite communications devices.
In 1957, Kroemer published the first complete proposal for a heterostructure transistor. His theoretical work showed that a heterotransistor could be superior to an ordinary transistor. In 1963, Kroemer and Alferov, working independently of each other, suggested how semiconductor heterostructures could be used in lasers. Lasers containing semiconductor heterostructures send out pulses of light that carry messages through optical fibers in modern telephone systems. Compact-disc players and bar-code readers also use such lasers.
Kroemer was born in Weimar, Germany, on Aug. 25, 1928. He received a Ph.D. degree in theoretical physics in 1952 from the University of Gottingen in what was then West Germany. He then worked in a number of research laboratories in West Germany and the United States. The American labs included RCA Laboratories in Princeton, New Jersey, where he worked from 1954 to 1957; and Varian Associates in Palo Alto, California, where he worked from 1959 to 1966. He served as professor of physics at the University of Colorado from 1968 to 1976. From 1976 to 2012, he was a professor of electrical engineering at the University of California at Santa Barbara. Kroemer died on March 8, 2024.
