It was recalled that, in the hetero-epitaxial growth of films with large misfits (linear mismatch strains of more than 1 to 2%) with respect to the underlying substrate, the generation of misfit and threading dislocations (tables 3 to 5) was normal for thicknesses that were much greater than the equilibrium critical thickness. It was noted that the experimental data suggested that the threading dislocation density in relaxed homogeneous buffer layers could be divided into 3 regimes. The first was an entanglement region, near to the film/substrate interface, that corresponded to threading dislocation densities of some 1010 to 1012/cm2. In the second region, there was a decrease in threading dislocation density that was inversely proportional to the film thickness. This applied to threading dislocation densities that ranged from some 107 to 109/cm2. In the third region, saturation or weak decay of the threading dislocation density occurred with further increases in film thickness. The typical saturation densities were of the order of 106 to 107/cm2. It was shown here that the reduction in the number of threading dislocations could be described in terms of the effective lateral motion of threading dislocations with increasing film thickness. An analytical model was developed which successfully predicted both the inverse-thickness scaling behavior, and the saturation of threading dislocation densities. It was concluded that long-range fluctuations, in the net Burgers vector content of the local threading dislocations, were a cause of saturation behavior.

Reduction of Threading Dislocation Densities in Homogeneous Buffer Layers. J.S.Speck, M.A.Brewer, G.Beltz, A.E.Romanov, W.Pompe: Journal of Applied Physics, 1996, 80[7], 3808-16

Table 3a

Possible Reactions between Threading Dislocations (generated by

surface half-loop nucleation) in the Epitaxy of Cubic Semiconductors

0 = annihilation, N = energetically unfavorable, X = repulsive interaction

Table 3b

Possible Reactions between Threading Dislocations (generated by

surface half-loop nucleation) in the Epitaxy of Cubic Semiconductors

0 = annihilation, N = energetically unfavorable, X = repulsive interaction

Table 4

Possible Reactions between Threading Dislocations (generated by island growth or fusion) in the Epitaxy of Cubic Semiconductors

0 = annihilation, N = energetically unfavorable, X = repulsive interaction

Table 5

Possible Reactions between Threading Dislocations (not covered

by previous two tables) in the Epitaxy of Cubic Semiconductors

0 = annihilation, N = energetically unfavorable, X = repulsive interaction