ABSTRACT
This chapter starts with a general discussion of the microstructure found in high optoelectronic quality GaN thin films, followed by a description of the crystalline structure of the GaN and of the most commonly used the substrates, SiC and sapphire. It discusses the atomic arrangement at the film/substrate interfaces, and the microstructure of the buffer layers and also describes some attempts at correlating the microstructure with the light emission. Since dislocations are disruptions of the lattice, they can be considered to be internal one-dimensional surfaces. If minority carriers are insensitive to the presence of a nearby surface, then it follows that they should be insensitive to dislocations. Doping, on the other hand, could either relax the dislocation strain by the chemical reaction of the dopants with the core and/or sharply decrease the depletion layer width by screening the dislocation core.
