Impact of dislocation motion on interdiffusion, structuring, and thermal transport at Ge–Si heterointerface

The roles of dislocation motion and interdiffusion on the interfacial morphology and thermal properties of the Ge–Si interface were elucidated using transmission electron microscopy, energy dispersive x-ray spectroscopy, and thermoreflectance measurements. Epitaxial Ge thin films deposited on Si (001) substrates by molecular beam epitaxy were annealed from 400 to 800 °C both in situ and ex situ in nitrogen to modify the interface morphology. Multiple transmission electron microscopy techniques monitored the evolution of defects and diffusion before and after different annealing treatments, revealing a strong correlation between dislocation motion and interdiffusion at the interface, producing a corrugated interface morphology. The characterization supports the fact that dislocations affect the interface structure by serving as vacancy sinks during their reconfiguration at elevated temperatures. Directed vacancy fluxes then enhance interdiffusion near dislocation cores, resulting in the periodic corrugation of the interface. Thermal measurements were performed to extract the thermal boundary resistance from the resulting interface morphologies produced by each annealing condition. Annealing resulted in increased thermal boundary resistance at the Ge–Si interface, largely attributed to alloy scattering becoming dominant as interdiffusion proceeds.