It was noted that, although several studies had successfully reduced the threading dislocation density in Ge films grown on Si, a high surface roughness remained problematic for nanoscale lithography and device fabrication. A low threading dislocation density and surface roughness were both achieved here by repeating a deposition–annealing cycle which consisted of the steps: low-temperature deposition, high-temperature and high-rate deposition, high-temperature H annealing. The root-mean-square roughness of the 3-cycle sample was in the range of 0.4 to 0.6nm for 10 x 10μm2 scan field atomic force microscopic images. The threading dislocation density as measured by plan-view TEM was 8 x 106 to 107/cm2 with a 1.44μm-thick sample. Moreover, a 4-cycle sample revealed further improvement in surface planarity and pit density in the atomic force microscopy images with a thickness of 2.38μm Ge. The high temperature and high rate Ge deposition combined with high-temperature H annealing efficiently reduced not only the threading dislocation density, but also the surface roughness.

Low Surface Roughness and Threading Dislocation Density Ge Growth on Si (001). D.Choi, Y.Ge, J.S.Harris, J.Cagnon, S.Stemmer: Journal of Crystal Growth, 2008, 310[18], 4273-9