MICRO-RAMAN CHARACTERIZATION OF MOLECULAR-BEAM EPITAXIAL GE HETEROLAYERS ON SI SUBSTRATES

Molecular-beam epitaxial germanium heterolayers on silicon are charact erized by micro-Raman spectroscopy. The samples are angle-lapped to pr obe the near-interface region. A small positive shift in the germanium phonon frequency is observed near the interface compared with the sur face of the 1 mum thick layer. This indicates that the misfit stress i s not relaxed completely in the as-grown layers. The samples are annea led at 700-degrees-C, a temperature higher than the growth temperature , and then the germanium peak shifts toward lower frequency near the i nterface. This would be due to both thermal stress and formation of an interfacial alloy layer by the interdiffusion. After annealing at 850 -degrees-C, the germanium peak shifts downward further because of the interdiffusion, and the peak due to the Si-Ge vibration is clearly obs erved near the interface.