The III-V nitride semiconductors have achieved a high degree of notoriety in the last few years.@footnote 1@ Light emitting devices based on double heterostructure InGaN/GaN films have been produced with light emission efficiencies exceeding incandescent lighting. Blue diode lasers with continuous operation for more than 10,000 hours using AlGaN/GaN/InGaN heterostructures have been reported and their commercial use is expected in the near future. The high optoelectronic performance of nitride semiconductors is related to an interesting microstructure, quite different from other semiconductors. Large dislocation densities are observed (~10@super 10@ cm@super -2@) and are associated with a columnar array of defect-free crystallites. The defect structure appears to play a key role in the relaxation of thermal stresses, typical in these materials, allowing the local growth of high quality heterostructures under otherwise unfavorable conditions. The nature of the substrate/thin film interfaces will be discussed, as well as the role of the buffer layer. Details of the dislocation arrangement and structure and correlation with light emitting properties will be presented for GaN thin films and for InGaN quantum wells.
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@footnote 1@ F. A. Ponce and D. P. Bour, Nature Vol. 386, 351 (1997).