Low surface roughness and threading dislocation density Ge growth on Si (0 0 1)

Although several recent studies have successfully reduced the threading dislocation density (TDD) in Ge films grown on Si, high surface roughness is still problematic for useful nanoscale lithography and device fabrication. In this work, we achieved both low TDD and surface roughness by repeating a deposition–annealing cycle consisting of the following steps: low temperature deposition, high temperature and high rate deposition, high temperature hydrogen annealing. The root-mean-square roughness of the 3-cycle sample is in the range of 0.4–0.6 nm for 10×10 μm2 scan field atomic force microscopy (AFM) images. The TDD measured by plan-view TEM is 0.8–1×107 cm−2 with a 1.44 μm thickness sample. Furthermore, a 4-cycle sample reveals further improvement in surface planarity and pit density in the AFM images with a thickness of 2.38 μm Ge. The high temperature and high rate Ge deposition combined with high-temperature hydrogen annealing efficiently reduces not only the TDD, but also the surface roughness.