Effect of isochronal hydrogen annealing on surface roughness and threading dislocation density of epitaxial Ge films grown on Si

We report the effect of hydrogen annealing on the surface roughness and threading dislocation density (TDD) of germanium (Ge) films grown on silicon (Si) substrates by reduced-pressure chemical vapor deposition (RPCVD). The surface roughness initially decreased with an increase in the annealing temperature. At annealing temperatures greater than 650 °C the film thickness varied owing to surface undulations, leading to an increase in the surface roughness. Although high-temperature annealing at 850 °C is effective for reducing TDD, the surface roughness of a 150-nm-thick Ge film annealed at 650 °C reaches a minimum value (~ 0.7 nm).