Heterostructures: From Physics to Devices and Back (A Personal Perspective)

Dr. Herbert KroemerUniversity of California, Santa BarbaraNobel Laureate, Physics, 2000Abstract
In semiconductor heterostructures the basic semiconductor itself– not just the doping– changes with position, and the transition region between the different semiconductorsplays an essential role in the operation of the device. The underlying physics is that in the transition region the forces acting on electrons and holes are no longer of purely electrostatic
origin, but contain an essentially quantum-mechanical component that is decoupled from the electrostatic forces. In fact, the resulting net forces can act in the same direction for electrons and holes, something fundamentally impossible with purely electrostatic forces.
The added forces give the device designer a powerful new degree of freedom that ranges from performance improvements
in already-existing devices, to the creation of devices that are fundamentally unachievable in homostructures, like the double-heterostructure laser. Today, all compound semiconductor devices of importance are heterostructure devices, and Si-Ge heterostructures have invaded mainstream silicon technology.
In addition to their importance in practical devices, heterostructures are playing a similarly dominant role in basic semiconductor physics. The best-known example–recognized by the 1998 Nobel Prize in Physics–is the fractional quantum Hall effect in the 2D electron gas at certain hetero-interfaces. Numerous other research areas in semiconductor
physics involve heterostructures in an essential way. Examples are nanostructures like quantum wires and quantum dots, superlattice Bloch Oscillators, and induced superconductivity in InAs quantum wells.Bio
Herbert Kroemer was born in 1928 in Weimar, Germany. He received a Doctorate in Theoretical Solid-State Physics
in 1952 from the University of Göttingen, Germany. Since then, he has worked on the physics and technology of semiconductors and semiconductor devices in a number of research laboratories in Germany and the U.S. Since 1976, he has been with the University of California at Santa Barbara.
Dr. Kroemer is the originator of several device concepts, including the heterostructure bipolar transistor, the double-heterostructure laser, and other heterostructure topics. During the '60s, he also worked on microwave device problems,
and in 1964 he was the first to publish an explanation for the Gunn Effect. With the emergence of molecular beam epitaxy in the mid-'70s, he returned to heterostructure devices, and he was one of the first to apply the emerging new technology to new and unconventional materials combinations, such as GaP-on-Si, GaAs-on-Si, and InAs/(Al,Ga)Sb structures, making several contributions to the development of MBE itself.
Dr. Kroemer is a Fellow of the IEEE and of the APS, and a Member of both the National Academy of Engineering and the National Academy of Sciences. He holds honorary doctorates from the Technical University of Aachen, Germany,
the University of Lund, Sweden, the University of Colorado, and the University of Duisburg-Essen, Germany. He has received numerous awards, most recently, in 2000, the Nobel Prize in Physics, "for developing semiconductor heterostructures used in high-speed and optoelectronics," and in 2002 the IEEE Medal of Honor.
His research interests continue to be in the physics and technology of semiconductor heterostructures.http://ee.usc.edu/munushian

Location: Ethel Percy Andrus Gerontology Center (GER) - 124

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