Formation of misfit dislocations during Zn-diffusion-induced intermixing of a GaInAsP/InP heterostructure

The microstructural degradation of a lattice-matched Ga0.28In0.72As0.61P0.39/InP heterointerface induced by Zn diffusion has been investigated using transmission electron microscopy. The localized interfacial stress caused by intermixing appears to create stacking faults in the Ga-mixed InP substrate, and dislocation tangles in the In-mixed GaInAsP layer. The observed results are attributed to the contrasted effect of tensile and compressive stresses upon the nucleation of dislocations from both sides of the GaInAsP/GaInP interface. As an evidence of the interface nucleation, we find a stacking fault at the tensile interface, which is bounded by a pair of partials having opposite Burgers vectors. A model is proposed to explain the strain relaxation in the intermixed region in terms of nucleation and splitting mechanisms of the paired dislocations.