Defects in epitaxial multilayers. III. Preparation of almost perfect multilayers

Almost perfect multilayers composed of epitaxial GaAs and Ga(As0.5P0.5) films have been prepared by chemical vapor deposition. The techniques used to enhance perfection were: (a) to use film thickness below that at which misfit dislocations are formed between layers; (b) to match the lattice parameter of the substrate to the lattice parameter of the multilayer taken as a whole; and (c) to use coherency, or misfit, strain to drive threading dislocations out of the sample. Specimens prepared using these techniques contained no dislocations to accommodate misfit between layers, and few dislocations to accommodate misfit between multilayer and substrate. The density of threading dislocations was < 104{plus 45 degree rule}cm2. This is at least 104 times smaller than the density of threading dislocations in the multilayers described in Parts I and II. These results establish that multilayers containing few dislocations can be made from materials with rather different lattice parameters. © 1976.