ABSTRACT
In the past few years, a class of wide energy bandgap semiconductors composed of III-nitride materials, primarily AlN, GaN, InN and related substitutional alloys composed of these compounds, have become of significant interest owing to their application in optoelectronics and high power RF devices. These materials have energy bandgaps in the range of Eg ∼1.9 to 6.2 eV. The materials crystallize in two phases, the hexagonal wurtzite and cubic zincblende polytypes. The wurtzite phases of AlN, GaN, and InN have direct bandgap of 6.2, 3.4, and 1.9 eV, respectively, and the cubic zincblende phases have bandgaps of Eg= 4.9, 3.2, and 1.7 eV, respectively [1]. The hexagonal wurtzite phase is the thermodynamically most stable structure of all the III-nitride polytypes and therefore, this polytype is the focus of virtually all research and development. Virtually all nitride-based devices of interest for commercial development are fabricated from hexagonal wurtzite GaN and related heterostructures. The wurtzite crystal structure is polar due to the charge redistribution between different atoms. A variety of RF devices can be fabricated from these materials, and these devices have improved performance over devices fabricated from standard materials such as Si, GaAs, and related compounds. The various devices that can be fabricated and their RF performance are reviewed in this chapter.
