Optical Properties Of Ingan-Based III-Nitride Heterostructures

With the recent progress in nitride growth technology, much research has been devoted to group III nitride wide-bandgap semiconductors for their applications, such as in UV visible light emitters, solar-blind UV detectors, and high-temperature and high-power electronic devices. In particular, InGaN-based structures are of great scientific interest for the commercialization of high-brightness visible UV LEDs [ 1 ] and cw violet current-injection laser diodes with lifetimes in excess of 10,000 hours [ 2 , 3 ]. The (In, ADGaN alloys, consisting of InN, GaN, and A1N, cover the entire visible to deep-UV region of the spectrum (1.9-6.2 eV). In spite of the poor structural quality (e.g., the large dislocation density) of nitride epitaxial layers compared with that of other III—V semiconductors, high-brightness LEDs [ 4 ] and cw violet laser diodes [ 5 ] based on InGaN structures have been constructed with high performance and high quantum efficiency [ 6 ]. Understanding the physical mechanisms giving rise to spontaneous emission and stimulated emission (SE) in InGaN-based structures is crucial not only from the viewpoint of scientific interest but also for designing practical devices. To explain the spontaneous and stimulated emission characteristics of InGaN-based structures, several groups have proposed different mechanisms (alloy potential fluctuations, quantum dot-like In phase separations, spontaneous polarization, strain-induced piezoelectric polarization, etc.); however, there has been much disagreement in the literature as to which of these mechanisms is dominant.