The equilibrium misfit dislocation density and strain profiles in reverse-graded hetero-epitaxial layers were calculated, using Si1− xGex/Si (001) as a model system. In these structures, there was a finite lattice mismatch at the substrate interface, and the composition was graded linearly in such a way that the lattice mismatch decreased with distance from this interface. Reverse-graded layers exhibited two distinct behaviours: termed unkinked and kinked. In the unkinked reverse-graded layer, the misfit dislocations were confined to a thin region near to the substrate interface, the residual strain was a linear function of distance from the interface and the strain underwent a sign reversal within the layer. The kinked reverse-graded layers exhibited a kink in the strain versus distance characteristic, and this kinked region contained an almost constant density of misfit dislocations.

Dislocations and Strain Relief in Reverse-Graded Semiconductor Layers. B.Bertoli, E.N.Suarez, F.C.Jain, J.E.Ayers: Semiconductor Science and Technology, 2009, 24[12], 125006