ABSTRACT
This chapter presents a basic description of figures of merit for microwave devices fabricated from wide bandgap materials. Wide bandgap semiconductors have received a great deal of attention as a nearly ideal material for the fabrication of high speed, high power transistors, particularly for cellular base station, broadcast, and high frequency radar applications. Wide bandgap materials such as silicon carbide and gallium nitride are known as such because their bandgaps are much larger than those of more conventional semiconductors such as silicon, germanium, or gallium arsenide. The ideal radio frequency (RF) power transistor has high current, high breakdown voltage, and a low “knee” voltage. Virtually all RF systems require active circuit elements for use as oscillators, and amplifiers. High resistivity substrates are most desirable for high frequency devices and result in improved direct current and RF performance for the transistor by better confining electrons to the conducting channel and reducing microwave losses.
