German-born physicist who, with Zhores Alferov and Jack S. Kilby, was awarded the 2000 Nobel Prize for Physics for their work that laid the foundation for the modern era of microchips, computers, and information technology.

After receiving a Ph.D. (1952) from Georg August University in Göttingen, Germany, Kroemer worked in the United States at RCA Laboratories (1954–57) in Princeton, New Jersey, and at Varian Associates (1959–66) in Palo Alto, California. In 1968 he became professor of electrical engineering at the University of Colorado at Boulder, and in 1976 he joined the faculty of the University of California at Santa Barbara.

In 1957 Kroemer carried out theoretical calculations showing that a heterostructure transistor would be superior to a conventional transistor, especially for certain high-frequency uses and other applications. (Most computer chips and other semiconductor components are made from one kind of material, whereas heterostructures are made of different materials.) Scientists later showed that he was correct—heterostructure transistors can operate at frequencies 100 times higher than conventional transistors, and they also work better as amplifiers. Alferov's research team in the Soviet Union applied Kroemer's theory, developing the first practical heterostructure electronic device in 1966. Alferov then pioneered electronic components, including the first heterostructure laser, which both men had proposed independently in 1963. Heterostructure devices made fibre-optic communications possible and are used in numerous everyday products, including computers and video players.