Use of misfit strain to remove dislocations from epitaxial thin films

Misfit strain can be used to drive threading dislocations out of epitaxial films and thus to improve their perfection. This process is influenced by film thickness, the orientation of the interface, the dimensions of the interface parallel to its plane, and the misfit between film and substrate. A simple theoretical model, and the experimental observations made on deposits of Ga(As, P) on GaAs, suggest that it is desirable for the film thickness to be small. This in turn implies that the misfit should be large. It should not, however, be large enough to cause dislocation nucleation. If the film is face-centered cubic, and the threading dislocations are uniformly distributed over the 〈110〉 {111} slip systems, then the most desirable interface orientations lie near {012} or {013}. If the Burgers vectors of the threading dislocations are not uniformly distributed then other interfaces may become desirable. Multilayers are able to remove threading dislocations more effectively than single films.