Kroemer, Herbert (1928-), a Germanborn 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 Ivanovich Alferov and the American electrical engineer Jack Kilby.
Kroemer was born in Weimar, Germany, in 1928. He received a Ph.D. degree in theoretical physics in 1952 from the University of Göttingen in what was then West Germany. He 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. In 1976, he became a professor of electrical and computer engineering at the University of California at Santa Barbara.
Kroemer's 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 does 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.
In 1957, he published the first complete proposal for a heterostructure transistor, showing that a heterotransistor could be superior to an ordinary transistor. Heterotransistors have proved useful in such applications as mobile telephones and satellite communications devices.
In 1963, Kroemer and Alferov, working independently, 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. They are also used in compact-disc players, bar-code readers, laser printers, and scientific instruments.