Poly-SiGe stacked gates with Ge content ([Ge])varying between zero and 100% have been fabricated using an industriel single-wafer machine. These poly-SiGe layers were characterised and fully integrated in a 0.18 pm CMOS process. Interdiffusion of Si and Ge upon subsequent annealing of the structure has been observed and studied. This interdiffusion effect was found to be responsible for the discrepancy observed between theoretical and practical values of the Ge workfunction ϕms evaluated from our electrical measurements and from those of different authors. A technique for the limitation of this interdiffusion effect has then been developped and is described.

We have used the strain sensitive tool two-dimensional reciprocal space mapping (2D-RSM) and high resolution rocking curves (HR-RC) to assess the effect of the layer thickness and the influence of low temperature Si buffer on the properties of fully relaxed Ge on Si (0 0 1). The samples were grown by chemical vapor deposition in an ASM commercial reactor. As complementary measurements we have employed secondary ion mass spectrometry (SIMS) for chemical analysis, cross sectional transmission electron microscopy for quality assessment, and finally atomic force microscopy (AFM) for investigating the surface roughness. The investigated samples have a thickness ranging from 0.25 to 5.0 μm. In addition and for a 5.0 μm thick Ge layer, an initial low temperature Si (LT-Si) template was grown before the Ge epitaxy. The results indicate that high quality fully relaxed Ge layers have been achieved using the adopted growth procedure. Most of the improvement in crystalline quality was observed for Ge layers with thickness up to 1.5 μm. Above this thickness the observed crystalline quality improvement was negligible. The LT-Si buffer observed to be disadvantageous for pure relaxed Ge growth.

We have fabricated light-emitting diodes on Si operating in the near-infrared. The active region of the p–i–n diodes consists of Ge/Si self-assembled quantum dots. The Ge islands were grown in an industrial 200 mm single-wafer chemical vapor deposition reactor. The photoluminescence and the electroluminescence of the islands are resonant in the spectral range around 1.4–1.5 μm wavelength. The electroluminescence is observed up to room temperature.

We have investigated the composition and the strain profile of Ge/Si self-assembled quantum dots. The quantum dots, grown by low-or high-pressure chemical vapor deposition, were covered by a silicon cap layer. The composition and the strain were measured by the selected area transmission electron diffraction of a single quantum dot. The self-assembled quantum dots exhibit a quadratic deformation. No lateral relaxation of the lattice is observed from the main part of the quantum dot. An average composition of Ge around 50% is deduced. The average composition is found dependent on the size of the islands. This composition is correlated to the photoluminescence energy.

Anodic oxides of SixGe1−x (0 ≤ x ≤ 1 ) alloys have been made by plasma assisted oxidation in a microwave frequency (2.45 GHz) reactor working in the constant current bias mode. Oxide films ∼15 – 40 nm (depending upon the Ge concentration) were obtained in 10 minutes without a temperature rise of the substrate of more than 100 °C. Detailed infrared absorption studies of the oxides enabled the Si-O-Si, Ge-O-Ge and Si-O-Ge vibrational modes to be identified, the strongest being at 1056, 858 and 1000 cm−1 respectively. These modes are associated with the O asymmetric stretch, their values are at lower wavenumbers than in bulk oxides due partly to ultraviolet radiation induced structural modification and partly to thin film optic effects. A statistical model for the different bonds present in SixGe1−xO2, when used to simulate the infrared spectrum does not predict the experimentally observed form, the Ge-O-Ge peak is in general too intense in the experimental spectrum. Auger electron spectroscopy profiling of the SixGe1−x oxides suggests that there is a build-up of Ge close to the surface/oxide interface so that when combined with the infrared data, we conclude that there is a GeO2 rich region at the surface/oxide interface. The oxide is, however, globally stoichiometric. Electrical measurements (C(V) and interface state density) were begun on metal-oxide-semiconductor (MOS) capacitors for Si1−xGex. oxides over the range of concentrations 0 ≤ x ≤ 1. Only Si1−xGex oxides with x≤0.15 appear to yield satisfactory MOS capacitor curves.

Amorphous GeO2 has been grown by plasma assisted anodic oxidation at temperatures ⩽100 °C. The growth kinetics can be explained in terms of a constant current anodization model. Infrared absorption spectroscopy has been used to characterize the transverse and longitudinal optic vibrational modes of the oxide network. Values are displaced with respect to bulk oxide due to geometrical optic effects and plasma induced network structure variation. In relaxed GeO2 we estimate the mean Ge-O-Ge bridging bond angle to be >123° and the full width at half peak height of the bond angle distribution is ∼14°. Electrical measurements on thin oxide capacitors suggest that in 25 nm oxides there are ⩽2×1011 negative charges cm−2 and negligible interface state densities.

Anodic oxides of Si x Ge 1-x (0 ≤ x ≤ 1) alloys have been made by plasma assisted oxidation in a microwave frequency (2.45 GHz) reactor working in the constant current bias mode. Oxide films ~15–40 nm (depending upon the Ge concentration) were obtained in 10 minutes without a temperature rise of the substrate of more than 100 °C. Detailed infrared absorption studies of the oxides enabled the Si-O-Si, Ge-O-Ge and Si-O-Ge vibrational modes to be identified, the strongest being at 1056, 858 and 1000 cm −1 respectively. These modes are associated with the O asymmetric stretch, their values are at lower wavenumbers than in bulk oxides due partly to ultraviolet radiation induced structural modification and partly to thin film optic effects. A statistical model for the different bonds present in Si x Ge 1-x O 2 , when used to simulate the infrared spectrum does not predict the experimentally observed form, the Ge-O-Ge peak is in general too intense in the experimental spectrum. Auger electron spectroscopy profiling of the Si x Ge 1-x oxides suggests that there is a build-up of Ge close to the surface/oxide interface so that when combined with the infrared data, we conclude that there is a GeO 2 rich region at the surface/oxide interface. The oxide is, however, globally stoichiometric. Electrical measurements (C(V) and interface state density) were begun on metal-oxide-semiconductor (MOS) capacitors for Si 1-x Ge x . oxides over the range of concentrations 0 < x < 1. Only Si 1-x Ge x oxides with x ≤ 0.15 appear to yield satisfactory MOS capacitor curves.

Direct nitridation of the silicon substrate using gaseous NO at 550–700°C, 10 mbar is studied using physical (SIMS, TEM, XPS) and electrical characterisations. The nitrogen profile can be tailored for the fabrication of thin nitrided oxides as in the case of implanted nitrogen. Degradation of the I(V) characteristics has been evidenced when the nitrogen amount increases.

Oxides of Sii-xGex alloys have been grown using the method of plasma assisted, anodic oxidation at temperatures < 100 degrees C. The growth kinetics have been analysed as a function of Ge concentration to obtain information on the O- ion mobility, mu, in the oxide. We observe mu(SiO2) < mu(GeO2) < mu(Sii-xGexO2) for 0.0 < x < 1.0. Infrared absorption spectroscopy has been used to examine the network bonding, it shows that the numbers of Si-O-Si, Si-O-Ge and Ge-O-Ge bonds do not follow those expected on the basis of simple statistics related to the relative concentrations of Si and Ge. Auger electron spectroscopy and secondary ion mass spectroscopy reveal that the anodic oxides are spatially inhomogeneous being composed of mixtures of SiO2, GeO2 and Sii-xGexO2, consistent with the results of infrared analysis. (C) 1999 Elsevier Science B.V. All rights reserved.

We report on the structural and optical properties of Ge/Si self-assembled quantum dots epitaxially grown on Si(001). The Ge islands are grown in an industrial 200 mm single-wafer chemical vapor deposition reactor. The surface density of the Ge islands is as much as 2×1010 cm−2. The islands exhibit a maximum photoluminescence at 1.55 μm wavelength. The photoluminescence energy is correlated to the three-dimensional quantum confinement energy and to the size and geometry of the clusters, as observed by cross-section transmission electron microscopy.