GROWTH OF A GE SI/GE(100) HETEROSTRUCTURE BY VERY-LOW PRESSURE CHEMICAL-VAPOR-DEPOSITION USING SI2H6 AND GEH4 GASES - PHOTOEMISSION AND LOW-ENERGY-ELECTRON DIFFRACTION STUDIES/

We present photoemission and low energy electron diffraction (LEED) re sults obtained on a Ge/Si/Ge(100) heterostructure grown by very low pr essure chemical vapour deposition of disilane (Si2H6) or germane (GeH4 ) on a Ge(100) 2 x 1 substrate. Both gases were catalytically dissocia ted at a hot tungsten filament. A thin (about 20 Angstrom thick) epita xic Si film is deposited by means of the CVD technique on an aromatica lly clean Ge(100) 2x1 substrate by exposing it at 300 degrees C to a d issociated Si2H6 gas phase. The obtained Si/Ge structure is then submi tted to a subsequent dissociated GeH4 exposure at 250 degrees C to ach ieve Ge deposition. Growth of the resulting Ge/Si/Ge(100) heterostruct ure is followed by means of X-ray photoemission spectroscopy, angle-re solved ultraviolet photoemission spectroscopy and LEED. The main and o riginal conclusion of our study is the possibility of Ge growth from a GeK4 gas phase on top of a thin epitaxic Si layer previously deposite d on Ge(100) from an Si2H6 gas phase. Such studies, performed in repro ducible ultrahigh vacuum conditions on the very first steps of interfa ce growth, should contribute to a better understanding and control of the various parameters involved in the gas source, molecular beam epit axial growth of forthcoming Si/Ge heterostructures.