Interaction between surface morphology and misfit dislocations as strainrelaxation modes in lattice-mismatched heteroepitaxy

Abstract

We show how strained layer heteroepitaxial systems can serve as model systemsfor the study of dislocation energetics and kinetics in semiconductors through theintroduction of strain-relieving misfit dislocation arrays. Such structures allowfundamental dislocation properties to be studied at carefully controlled stressesin the range 107–109 Pa. A parallel strain relaxation mode in strainedheterostructures is via coherent islanding or surface roughening of the epitaxiallayer. This mechanism acts both in competition and in cooperation with injectionof misfit dislocations, and provides a further degree of control for study of thefundamental energetic and kinetic properties of dislocations. Using ultra-sensitivein situ wafer curvature measurements of stress during molecular beam epitaxygrowth of GexSi1−x/Si heterostructures, the relative contributions of surfaceroughening and dislocation injection to strain relaxation may be qualitatively andquantitatively assessed. In addition, a new strain-stabilized morphology,‘quantum fortresses’, comprising cooperative island nucleation around shallowstrain-relieving pits, is identified during Ge0.3Si0.7/Si(100) heteroepitaxy. Thisconfiguration has potential application to nanoelectronic device architectures.