Relaxation Dynamics and Threading Dislocations in ZnSe and ZnS^sub y^Se^sub 1-y^/GaAs (001) Heterostructures

The design of lattice-mismatched semiconductor devices requires a predictive model for strains and threading dislocation densities. Previous work enabled modeling of uniform layers but not the threading dislocations in device structures with arbitrary compositional grading. In this work we present a kinetic model for lattice relaxation which includes misfit-threading dislocation interactions, which have not been considered in previous annihilation-coalescence models. Inclusion of these dislocation interactions makes the kinetic model applicable to compositionally graded structures, and we have applied it to ZnSe/GaAs (001) and ZnS^sub y^Se^sub 1-y^/GaAs (001) heterostructures. The results of the kinetic model are consistent with the observed threading dislocation behavior in ZnSe/GaAs (001) uniform layers, and for graded ZnS^sub y^Se^sub 1-y^/GaAs (001) heterostructures the kinetic model predicts that the threading dislocation density may be reduced by the inclusion of grading buffer layers employing compositional overshoot. This "dislocation compensation" effect is consistent with our high-resolution x-ray diffraction experimental results for graded ZnS^sub y^Se^sub 1-y^/GaAs (001) structures grown by photoassisted metalorganic vapor-phase epitaxy.[PUBLICATION ABSTRACT]