Novel group IV alloy semiconductor materials

Citation

He, Gang (1997) Novel group IV alloy semiconductor materials. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/tett-t906. https://resolver.caltech.edu/CaltechETD:etd-07222008-093116

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Novel group IV alloy semiconductor materials were investigated to explore their potential applications in silicon-based optoelectronic devices and high speed electronic devices. One system investigated is the ternary [...] alloy. Epitaxial [...] alloy films with tin and carbon concentrations of up to y=0.02 (x=0.5) were synthesized successfully on silicon substrates by molecular beam deposition followed by solid phase epitaxy. The effect of strain compensation from tin and carbon greatly reduced the epitaxial strain and produced dislocation-free heteroepitaxial films on silicon substrates which may enable high-speed silicon-based low-strain heterojunction devices. Another system investigated is the binary [...] alloy. Tight-binding and pseudopotential calculations predicted that [...] has a direct energy band gap that is continuously tunable in the mid and long wavelength infrared region [...] for tin concentrations in the range of x=0.2 to x=0.6, which makes it an attractive material system for silicon-based integrated infrared optoelectronic devices. Epitaxial [...] films were synthesized successfully on silicon substrates by conventional molecular beam epitaxy with tin concentrations of up to x=0.2, beyond which severe tin surface segregation caused a breakdown of epitaxy. To overcome the problem of surface segregation, ion-assisted molecular beam epitaxy was studied. Low energy, high flux ion irradiation of the sample surface during growth greatly reduced tin surface segregation and achieved tin concentrations up to x=0.34. An analytical model was developed to describe surface segregation during energetic beam epitaxial growth and was applied to ion-assisted molecular beam epitaxy growth of [...]. Infrared absorption measurements of the [...] samples showed that the decrease of [...] energy band gap with increasing tin concentration was much faster than predicted by tight-binding and pseudopotential calculations. The measured absorption onset was as low as 0.25 eV for a tin concentration of x=0.15, and the measured absorption strength was comparable to the typical direct band gap infrared semiconductors such as InAs and InSb. The results of the absorption measurements suggest that full access to the tunable [...] energy band gap from mid infrared to far infrared may be obtained with a maximum tin concentration of about x=0.25 instead of x=0.6 as predicted by tight-binding and pseudopotential calculations.

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