Ultrafast phenomena in semiconductor devices

The basic concepts of high-speed semiconductor performance are discussed, along with the technologies which allow investigations on a picosecond time scale. Ultrafast processes in semiconductors are examined in terms of an idealized circuit containing a block of semiconductor and a load capacitor. Methods of minimizing the transit time are analyzed and the rise in importance of nonequilibrium transport considerations is noted, as well as the use of optoelectronics for studying the electronic behavior of ultrafast semiconductors. Velocity overshoot is observable with subpicosecond optoelectronic switching techniques, and consequently so are space-charge effects that determine the current-voltage characteristics of short channel devices. Attention is given to molecular beam epitaxy and CVD manufacturing techniques of GaAs devices, and applications for high speed test instrumentation are reviewed.