College of Engineering, University of California, Santa Barbara, United States
2000 Nobel Physics Laureate.
Kroemer is a pioneer in the field of semiconductor devices. He was the first to propose the use of heterojunctions for injection lasers and transistors, and he developed semiconductor heterostructures that are used in high-speed opto-electronics. His current research focuses on semiconductor hybrid structures and current transport in semiconductor superlattices.
In his research. Prof. Kroemer has always preferred to work on problems that are one or two generation ahead of established mainstream technology. In the mid-`50-s, he was the first to point out that great performance advantages could be gained in various semiconductor devices (initially bipolar transistors) by incorporating what is now called heterostructures into the devices. Most notably, in 1963 he proposed the concept of the double-heterostructure laser, the central concept in the field of semiconductor lasers, without which that field would simply not exist. These ideas were far ahead of their time, and required the development of modern epitaxial growth technology before they could become mainstream technologies, in turn providing a great stimulus towards the development of these technologies.
His current research continues to involve this materials combination, in a number of projects at the forefront of the heterostructure field, which involve high-performance devices, materials research, and new areas of solid-state physics.
Kroemer turned to experimental work and became one of the early pioneers in molecular beam epitaxy, concentrating from the outset on applying the technology to untried new materials systems, such as GaP and GaAs on Silicon. Since 1985, his work has shifted towards the “6.1Å group” of materials, InAs, GaSb, and AlSb, a group where he saw great opportunities for future devices. His current research continues to involve this materials combination, in a number of projects at the forefront of the heterostructure field, which involve high-performance devices, materials research, and new areas of solid-state physics.
This current research is dominated by two quite different topics: (a) superconductor-semiconductor hybrid structures involving InAs-AlSb quantum wells contacted by superconducting niobium electrodes. In such structures, the superconducting electrodes in essence induce superconductivity in the semiconductor. Of all semiconductors, InAs is the best material for the construction of such devices. With its existing leadership in InAs quantum well technology, Prof. Kroemer's group was in an unique position to exploit these possibilities. (b) A second topic involves the current transport in semiconductor superlattices under the influence of high electric fields perpendicular to the superlattice planes, fields sufficiently strong that they lead to so-called Bloch oscillations within the tilted energy bands. Theory predicts that such structures should be capable of serving as oscillators—commonly called Bloch oscillators—up to frequencies in the terahertz regime.
Kroemer's research—part of a team effort at UCSB—is directed towards developing the in-depth theoretical understanding of the problems that must be overcome to convert the Bloch oscillator from a theoretical speculation to technological reality.
J.J. Ebers Award of the Electron Devices Group of the IEEE (1973),
Heinrich Welker Medal of the International Symposium on GaAs and Related compounds (1982),
National Lecturer, IEEE Electron Devices Society (1983),
Honorary Doctorate in Engineering, Technical University of Aachen, Germany (1985),
Jack Morton Award of IEEE (1986),
Donald W. Whittier Chair in Electrical Engineering (1986),
Alexander von Humboldt Research Award (1994),
National Academy of Engineering (1997),
Nobel Prize in Physics (2000).
H. Kroemer, “Quasi-Electric and Quasi-Magnetic Fields in Non-Uniform Semiconductors,” Symposium on the Role of Solid State Phenomena in Electric Circuits, Polytechnic Institute of Brooklyn, 1957, Polytechnic Institute of Brooklyn, pp. 143-153. Re-published in RCA Review, vol. 18, pp. 332-342, 1957.
H. Kroemer, “A Proposed Class of Heterojunction Injection Lasers,” Proc. IEEE, vol. 51, pp. 1782-1783, 1963.
H. Kroemer, “Solid State Radiation Emitters,” U.S. Patent 3,309,553, March 14, 1967. (Filed Aug. 16, 1963).
H. Kroemer, “Heterostructures for Everything: Device Principle of the 1980's?,” Jpn. J. Appl. Phys., vol. 20 (Supplement 20-1), pp. 9-13, 1981.
H. Kroemer, “Heterostructure Bipolar Transistors and Integrated Circuits,” Proc. IEEE, vol. 70, pp. 13-25, 1982.
M. Thomas, H.-R. Blank, K. C. Wong, H. Kroemer, and E. Hu, “Current-voltage characteristics of semiconductor-coupled superconducting weak links with large electrode separations,” Phys. Rev. B, vol. 58, pp. 11676-11684, 1998.
H. Kroemer, “Large-amplitude oscillation dynamics and domain suppression in a superlattice Bloch oscillator,” cond-mat/0009311.