Dopant segregation mechanism in general involves the chemical effect, the Fermi-level effect, and the effect of the junction carrier concentrations. Satisfactory fits of available B distribution profiles in GexSil−x/Si heterostructures have been obtained using such a model, but with the chemical effect not important. The Fermi-level effect determines the difference in the ionized B solubilities in GexSil−x and Si. The singly-positively charged crystal self-interstitials I+ governs the boron diffusion process. The junction carrier concentration affects the concentration of I+ and solubility of B in the region and hence controls B diffusion across the heterojunction.

Surface termination of Ge(100) and Si(100) was investigated after diluted HF (DHF) solution dipping. On the Ge(100) surface as picked up from DHF, Ge-hydride was observed only in the HF concentration (CHF) region above 10%. The adsorbed fluorine increased with increasing CHF, and the concentration reached around 1014 cm−2 at the CHF of 40-50%. In the case of the DHF dipped Si(100) surface, Si-hydride and hydrophobicity against both DHF and deionized water (DIW) were observed for all the conditions studied, while the fluorine concentration increased and saturated to about 1014 cm−2 in the CHF region above 15%. Hydrophobicity against DHF was observed in the CHF region of 10-30%, but degraded below 5% and above 30%. By transferring the DHF dipped Ge(100) into DIW, hydrophobicity appeared within a few seconds and then was degraded with increase of DIW dipping time. The degradation proceeded slower after dipped in higher concentration DHF. Corresponding to the degradation, it was observed that the total amount of the adsorbed fluoride was gradually decreasing, while the Ge-hydride coverage scarcely decreased. From these results, hydrophobicity of Ge(100) seems to be attributed not only to the hydrogen termination but also to the fluoride adsorption, which is much different from the case of Si(100).

Processing of silicon-based heterojunction devices is severely constrained by the relaxation of strained epitaxial layers. Generally the equilbrium critical thickness cannot be exceeded if high-temperature process steps such as oxidation and diffusion are performed. In this paper, we report on the beneficial effects of small amounts of carbon ( 0.2%) added to germanium-silicon epitaxial layers. We will show that such low concentrations result in a substantial decrease of boron diffusivity and strain relaxation. We will also report on the fabrication of GexSil-x-yCy heterostructure MOS capacitors with a channel thickness of 300 A° and a maximum germanium fraction of 50% A thermal oxidation at 800 ‘C was performed resulting in good C(VG) characteristics along with improved hole confinement.

Mobilities in Si1-x-yGex Cy layers were measured using mesa etched Van der Pauw structures for alloy layers with 0 < x < 0.30 and 0 < y < 0.02 and doping levels of 1015 < N < 1018 cm-3. Mobilities in Si1-x-yGex Cy layers with x = 0.27 were found to approach Si mobilities for both μn and μp.While electron mobilities in phosphorous-doped SiGeC decrease with doping concentration, hole mobilities in boron-doped SiGeC increase with doping level, indicating ionized impurity scattering is not dominant for μp over the temperature range studied.

We have performed intensive theoretical studies on the ordered Si 4C phase which has been proposed first by Riicker et al. [Phys. Rev. Lett.72, 3578 (1994)] and which recently has been reportedly synthesized by Kouvetakis et al. [Appl. Phys. Lett.72, 930(1998). We calculate structural parameters which are significantly different from experimental values, and an IR spectrum with a peak position very similar to their experiment but a much narrower width. We suggest that the experimental findings might be consistent with the assumption of a system of Si4C sections/crystallites and other Si–C structures embedded in a Si matrix.