Effects of hydrogen on the formation of SiGe/Si heterostructures
In this report, we review and discuss our results obtained on the surface segregation of Ge atoms and surfactant effects of hydrogen atoms in Si overlayer growth on Ge/Si(100) by gas-source molecular beam epitaxy (GSMBE) using GeH/sub 4/ and Si/sub 2/H/sub 6/. The layer-by-layer growth rate of the Si overlayers was observed in-situ by reflection high-energy electron diffraction (RHEED) intensity oscillation periods.
Study of reaction and electrical properties at Ti/SiGe/Si(100) contacts for ultralarge scale integrated applications
Solid-phase reaction, Schottky barrier heights and contact resistivities at the interface of Ti/Si0.8Ge0.2/Si(100) systems have been investigated. At annealing temperatures below 300 °C, Ti atoms preferentially react with Si atoms. Ge atoms start to react with Ti above 400 °C and C54–Ti(Si1−yGey)2 with a fraction of y=0.12 is formed by annealing at 650 °C. The annealing behavior of Schottky barrier heights suggests that the Ge composition of SiGe layers at the interface is Si-rich, which is consistent with the results on the interfacial reaction. For both n- and p-SiGe, the Schottky barrier heights lower than those of Ti/Si(100) are obtained at 650 °C, which is considered to be related to the reaction product such as C54–Ti(Si1−yGey)2. The contact resistivities smaller than those expected from the Schottky barrier heights are obtained for p+-SiGe at 580 °C. The sheet resistance of Ti/Si0.8Ge0.2/Si(100) and Ti/Ge(100) systems decreases at annealing temperatures above 550 °C and the values are as small as t...
Ge Segregation during molecular beam epitaxial growth of Si1-xGex/Si layers
Abstract The growth of pseudomorphic Si 1− x Ge x layers (0.08 ⩽ x ⩽ 0.33) on Si (100) was studied by means of secondary ion mass spectroscopy and Rutherford backscattering spectrometry with glancing angle detection. The interfaces under growth conditions for epitaxy (substrate temperatures between 470 and 560 °C) were never atomically sharp but showed asymmetric smearing of the germanium towards the surface. The segregation is characterized by an inverse slope in the germanium profile of 17 nm per decade. The total amount of segragated germanium corresponds to between 0.2 and 0.5 monolayer. At lower temperatures the layers become rough, decreasing the crystalline quality, however, the interfaces as detected by secondary ion mass spectroscopy become much sharper. It is proposed that the smearing is due to a germanium ad-layer that is formed during the Si 1− x Ge x deposition and is incorporated slowly during further silicon growth.