Quasi-medium energy ion scattering spectroscopy observation of surface segregation of Ge δ-doped layer during Si molecular beam epitaxy

We have observed the behavior of Ge delta-doped layers fabricated by molecular beam epitaxy (MBE) on an Si(001) substrate and the surface segregation of Ge atoms from delta-doped layers during a top Si buffer layer growth using quasi-medium energy ion scattering spectroscopy. We have found that the Ge atoms segregate to the surface even at a low substrate temperature of 300 degrees C. This result is in contrast to the solid phase epitaxy case where Ge atoms diffuse around the interface. For MBE growth, at a substrate temperature of 600 degrees C, the surface segregation was reduced. The distribution of Ge atoms is widely spread in the subsurface region. This result indicates that the Ge atoms are incorporated in the Si buffer layer with mixing by Si atoms. (C) 1997 Elsevier Science B.V.