Surfactant-mediated epitaxy of relaxed low-doped Ge films on Si(001) with low defect densities

Fully relaxed, high-quality Ge layers were grown directly on Si(001) substrates by surfactant-mediated epitaxy at high temperature with large Sb flux. We attribute the low dislocation densities in our films to an abrupt strain relief via the formation of a regular array of 90° dislocations at the interface during the initial, microrough stage of growth. This mechanism of abrupt strain relaxation occurs exclusively under high Sb coverage at temperatures ∼700°C. The high growth temperature also enhances Sb segregation leading to a low background doping level of only (3–4×1016)cm−3. Thus, we regard surfactant-mediated epitaxy of relaxed Ge on Si(001) as a promising candidate for device application.