ABSTRACT
This chapter deals with several important aspects of mismatched heteroepitaxial growth: the critical layer thickness, lattice relaxation and the introduction of dislocation defects, and the dynamics of dislocation reactions and removal from thick, mismatched layers. In thick, lattice-mismatched heteroepitaxial layers, most of the mismatch may be accommodated by misfit dislocations during growth, even if kinetic factors are important. A possible mechanism for the introduction of misfit dislocations is the homogeneous nucleation of half-loops at the surface. In many heteroepitaxial semiconductors, the observed lattice relaxation can only be explained by invoking either the nucleation of new dislocations or dislocation multiplication. Some simple lattice relaxation mechanisms have already been considered briefly, in the sections on the critical layer thickness, dislocation nucleation, and dislocation multiplication. Heteroepitaxial semiconductors grown on vicinal substrates generally exhibit a crystallographic tilt with respect to the underlying substrate. Often heteroepitaxial layers have thermal coefficients of expansion very different from their substrates.
