IN-SITU OBSERVATION OF GAS-SOURCE MOLECULAR-BEAM EPITAXY OF SILICON AND GERMANIUM ON SI(001)

We have observed the development of the surfaces during gas-source gro wth of silicon and germanium in an elevated temperature ultrahigh vacu um scanning tunneling microscopy (STM), with near-atomic resolution un der a range of temperature and flux, which are the two dominant parame ters, and applied atomistic modeling to the structures seen by STM to enable us to give confident interpretation of the results. A key role in the growth of silicon and germanium on Si(001) from disilane and ge rmane, respectively, is played by the surface hydrogen. The growth of germanium follows a similar path to that of silicon for the first few monolayers, after which the strain becomes relieved by periodic trench es, and eventually by a combination of faceted pits and clusters, both of which nucleate heterogeneously at surface defects. Understanding t hese processes is crucial to controlling the self-assembled Ge/Si quan tum structures. (C) 1998 American Vacuum Society.