Herbert Kroemer

Herbert Kroemer was a German-American physicist whose semiconductor heterostructure ideas helped establish the foundations of high-speed electronics and optoelectronic devices. He shared the 2000 Nobel Prize in Physics for developing semiconductor heterostructures used in high-speed and optoelectronic devices.

Semiconductor heterostructure: A structure formed by joining semiconductor layers with different compositions and electronic properties. Kroemer’s central proposal used interfaces between different semiconductors to control charge carriers.
Heterojunction bipolar transistor: A bipolar transistor whose emitter and base use semiconductors with different band gaps. Kroemer proposed this transistor architecture to improve injection efficiency and high-frequency performance.
Semiconductor epitaxy: The growth of a crystalline semiconductor layer on a crystalline substrate in a defined orientation. Precise epitaxial layers made the heterostructures Kroemer envisioned experimentally realizable.
Zhores Alferov: A Soviet and Russian physicist who developed semiconductor heterostructures and shared the 2000 Nobel Prize in Physics. Alferov independently advanced heterostructure devices and shared the Nobel award with Kroemer.
Band gap: The energy range separating a solid’s valence band from its conduction band. Different band gaps let heterostructures confine carriers and shape their energies.
High-electron-mobility transistor: A field-effect transistor that uses a semiconductor heterostructure to form a high-mobility electron channel. The device exploits interface confinement to achieve fast operation, a goal central to Kroemer’s work.
Molecular-beam epitaxy: A vacuum technique for growing crystalline thin films by directing beams of atoms or molecules onto a substrate. Its precise layer control helped turn heterostructure concepts into nanoscale devices.
Jack Kilby: An American electrical engineer who invented the integrated circuit and shared the 2000 Nobel Prize in Physics. Kilby received the same prize for integrated circuits, a distinct contribution to semiconductor technology.
Heterojunction: An interface between two semiconductors with different compositions or electronic properties. Kroemer showed how carefully designed heterojunctions could improve semiconductor devices.
Double heterostructure: A narrow-band-gap semiconductor layer sandwiched between wider-band-gap semiconductor layers. This arrangement confines both carriers and light, making efficient semiconductor lasers possible.

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