31. Group III Nitrides

Optical, electrical, mechanical, and thermal properties of group III nitrides, inclusive of AlN, GaN, InN and their ternary and quaternary alloys, are discussed. The driving force for group III nitride semiconductors is their important applications in optoelectronics, microwave amplifiers, and high voltage power switches. Owing to the aforementioned applications, the fundamental properties of each III nitride binary, as well as the alloys that have been acquired, are discussed in this chapter. In general, an appropriate assessment of the material properties for any material is not straightforward to begin with and the nitride family is no exception, particularly considering that group III nitrides are prepared on foreign substrates as low-cost native substrates are not yet available. Understandably, precise measurements of the mechanical, thermal, electrical and optical properties of the semiconductor nitride family are imperative for further advances. Notwithstanding the great progress that has already been made to further understand and exploit group III nitrides, especially GaN, reliable data for AlN and InN are still in the state of evolution, and naturally the subject of some controversy. This is, in part, a consequence of measurements having been performed on samples of widely varying quality. When possible, the spurious discrepancies have been disregarded. For some materials, too few measurements are available to yield a consensus, in which case the available data are simply reported. Defects in group III nitrides as well as GaN-based nanostructures are also discussed.