Growth of a Ge/Si/Ge (100) heterostructure by very low pressure chemical vapour deposition using Si 2H 6 and GeH 4 gases—photoemission and low energy electron diffraction studies

Abstract

We present photoemmision and low energy electron diffraction (LEED) results obtained on a Ge/Si/Ge (100) heterostructure grown by very low pressure chemical vapour deposition of disilane (Si 2H 6 or germane (GeH 4 on a Ge(100) 2×1 substrate. Both gases were catalytically dissociated at a hot tungsten filament. A thin (about 20 Å thick) epitaxic Si film is deposited by means of the CVD technique on an atomatically clean Ge(100) 2×1 substrate by exposing it at 300 °C to a dissociated Si 2H 6 gas phase. The obtained Si/Ge structure is then submitted to a subsequent dissociated GeH 4 exposure at 250°C to achieve Ge deposition. Growth of the resulting Ge/Si/Ge (100) heterostructure is followed by means of X-ray photoemission spectroscopy, angle-resolved ultraviolet photoemission spectroscopy and LEED. The main and original conclusion of our study is the possibility of Ge growth from a GeH 4 gas phase on top of a thin epitaxic Si layer previously deposited on Ge (100) from an Si 2H 6 gas phase. Such studies, performed in reproducible ultrahigh vacuum conditions on the very first steps of interface growth, should contribute to a better understanding and control of the various parameters involved in the gas source, molecular beam epitaxial growth of forthcoming Si/Ge heterostructures.