Trapping threading dislocations in germanium trenches on silicon wafer

We show that Ge epilayers on Si substrates with trenches filled by Ge at a different temperature have very low threading dislocation density compared to blanket Ge epilayers on Si substrates. In cross-sectional transmission electron microscopy, dislocations at the trench edges are observed to extend to the film surface, which is in agreement with the results of etch pit density measurements where two rows of etch pits are observed at the trench edge. This indicates an appreciable dislocation sink, which unlocks the potential of providing high quality Ge-on-Si virtual substrates for growing lattice matched III-V photovoltaics.