A computational approach was presented for the determination of the equilibrium misfit dislocation density and strain in a semiconductor heterostructure with an arbitrary compositional profile. It was demonstrated that there was good agreement between the computed results and known analytical solutions for heterostructures containing a single linearly graded layer or a single uniform composition layer. Calculations were made of the dislocation density and strain profiles in SiGe/Si(001), InGaAs/GaAs(001), and ZnSSe/GaAs(001) heterostructures; each containing a uniform composition layer (uniform layer) on a linearly graded buffer layer (graded layer). The density of misfit dislocations in the graded layer was inversely proportional to its grading coefficient and was unchanged by the presence of the uniform layer, but the dislocated thickness increases with the uniform layer thickness. If the uniform layer was sufficiently thick, misfit dislocations will exist throughout the graded layer, but additional misfit dislocations were not produced in the uniform layer. The biaxial strain in the uniform layer was inversely proportional to its thickness and was unchanged by the graded layer. Calculations were also made of the equilibrium configuration in a convex exponentially-graded SiGe/Si(001) layer in which the misfit dislocation density tapered with distance from the interface. Other non-linear grading profiles offered opportunities for tailoring the misfit dislocation density and strain profile.

Misfit Dislocation Density and Strain Relaxation in Graded Semiconductor Heterostructures with Arbitrary Composition Profiles. B.Bertoli, E.N.Suarez, J.E.Ayers, F.C.Jain: Journal of Applied Physics, 2009, 106[7], 073519