Misfit dislocations in (001) semiconductor heterostructures grown by epitaxy

The epitaxial growth and the relaxation of lattice mismatched heterostructures is discussed in terms of misfit dislocations. Two experimental cases are studied: (i) a GaSb/GaAs system perfectly relaxed by a misfit dislocation network characterised as a square array of Lomer dislocations. These misfit dislocations are created by a periodic mechanism resulting from the island growth of GaSb on GaAs. They induce a total accommodation of the lattice mismatch. They are the most efficient and natural misfit dislocations of the (001) interface; (ii) a GaAs/InP system which is also relaxed by a randomly distributed misfit dislocation network. In this case the density of conventional misfit dislocation at the level of the interface is too low to explain the accommodation of the lattice mismatch. In addition to the misfit dislocations, other crystalline defects, such as clouds of point defects, seem to play a role in the relaxation of the misfit stress.