Surfactant-mediated epitaxy of high-quality low-doped relaxed germanium films on silicon (001)

Direct growth of relaxed Ge layers on Si(001) substrates was achieved using Sb as a surfactant. Deposition of Ge at substrate temperatures around 670 °C under large Sb flux resulted in complete compensation of lattice mismatch via a regular array of 90° dislocations at the interface. A residual 0.20% tensile strain is found caused by thermal mismatch between Ge and Si. The density of defects threading through the Ge films is as low as 5 × 107 cm− 2. This is ascribed to an abrupt strain release during the initial micro-rough growth phase, which occurs only under the selected growth conditions. We also observed n-type Sb background doping levels in the Ge layers well below 1017 cm− 3 presumably related to an enhanced Sb surface segregation due to the high growth temperature. Such relaxed Ge films grown by surfactant-mediated epitaxy on Si(001) open attractive perspectives for integration of novel Ge devices into mainstream Si technology.