GAAs High-Speed Devices: Physics, Technology, and Circuit Applications

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HOT-ELECTRON TRANSISTORS AND NOVEL DEVICES

As semiconductor devices shrink in size and internal fields rise, a large number of carriers in the active regions of the device during its operation are in states of high kinetic energy [Con67]. At a given point in space and time the velocity distribution may be narrowly peaked, which is what is meant when one speaks of “ballistic” electron packets [Lur90]. At other times and locations, the nonequilibrium electron ensemble can have a broad velocity distribution, usually taken to be maxwellian and parametrized by an effective electron temperature T_e > T, where T is the lattice temperature. hot-electron phenomena have become important, and they have successfully been applied to semiconductor devices.

The history of hot-electron transistor development can be traced back to the early 1960s “metal-base transistors” [Sze81]. In those days the performance of these devices was severely limited to current gains of less than unity [Sze81], so interest in their development quickly declined. With the continuing advancements in device fabrication, equipment, and processing technology, interest in the metal-base transistors resumed. In the late 1970s a hot-electron transistor (HET) in silicon was developed by Shannon [Sha79]; it had a Schottky barrier emitter and Camel diode collector. The high emitter capacitance of the Schottky barrier led Shannon to fabricate an alternative HET with both a Camel diode emitter and collector, resulting in an all ...