Sputter Epitaxial Growth of Flat Germanium Film with Low Threading-Dislocation Density on Silicon (001)

摘要

Fast epitaxy of Ge on Si(001) was realized by DC sputtering at 2.1 nm· s~(-1) and 360°C; the resulting film was optically flat without a cross-hatch structure. After annealing at 700°C, 90°-full-edge dislocations dominated the Ge-Si interface and the threading-dislocation density (TDD) of the Ge film was below 10~4 cm~(-2), which is three orders of magnitude lower than the value of Ge films prepared by other methods. The extremely low TDD might be attributable to the spaces vacated by desorbed Ar within the film that served as dislocation sinks during sputtering. Acceptor-band conduction, which was at 0.02 eV above the valence band and was induced by dislocations, was observed with a hole mobility of 3-10 cm~2· V~(-1) · s~(-1) in the film prepared without annealing. After annealing at 700°C, the ionized-defect scattering in the film was considerably decreased and a mobility of 1180 cm~2· V~(-1)· s~(-1) was obtained. The direct band gap energy of the film prepared without annealing was 0.81 eV, and became 0.79 eV after annealing.