Chapter 3 - Defect engineering in III-nitrides epitaxial systems

Abstract

This chapter reviews the common crystallographic defects observed in the GaN and related Ill-nitride systems based on the electron microscopy results. All foreign substrates for the GaN epitaxy have a high mismatch in lattice parameters, thermal expansion, and chemical composition with the GaN layer. Among a large number of different foreign substrates tested for the GaN deposition, sapphire and 6H silicon carbide show the best results in terms of the layer quality. The mismatch in lattice parameters and thermal expansion coefficients between the GaN and these substrates is high leading to a generation of the high density of defects at the epilayer–substrate interface. The lattice mismatch between the GaN and SiC is about 2%, but it is even higher in case of the GaN layers grown on sapphire being about 16% and 30% for c- or a-facet of sapphire, respectively. The chapter also discusses annihilation, which is mainly a growth-related process.