The collector function in semiconductor devices

The functional behavior of the collector part of an amplifying three terminal electronic device is reviewed, relevant for transport and collection of carriers. The important properties are analyzed, with emphasis on III-V materials. The resulting demands are deduced, and conventional as well as unconventional solutions in the case of unipolar devices (FETs) and bipolar devices (HBTs) are presented. They include bandgap and doping profiling, heterojunction- and Schottky-collectors. Not considered are thermal stability problems and further DC phenomena, relevant for high-power devices.