Properties and Applications of Crystalline Si1-x-yGexCy alloys

We have used both electrical and optical characterization methods to study the effect of carbon on the valence band offset of compressively strained Si1-x-yGexCy / Si (100) heterojunctions grown by Rapid Thermal Chemical Vapor Deposition (RTCVD) with substitutional C levels from 0% to 2.5%. Our work indicates that the change in the bandgap of Si1-x-yGexCy as carbon is added is entirely accommodated in the valence band. We also propose a simple model to predict the change of band structure with the incorporation of C. We have also investigated the transport properties of holes in Si1-x-yGexCy channels by fabricating a compressively strained Si1-x-yGexCy/Si (100) modulationdoped structures. We found that hole mobility decreased as more C was added. The decrease in hole mobility was determined to be caused by C-related defects, not by change in the effective mass of holes as C was added. Finally, we demonstrated an application of crystalline Si1-x-yGexCy by growing polycrystalline Si1-x-yGexCy and used it as part of a polycrystalline gate structure for PMOS devices. The results showed that the use of carbon in polycrystalline Si1-x-yGexCy suppressed boron penetration across the gate oxide. No effects of gate depletion with the use of poly-Si1-x-yGexCy were observed. Our work suggests that the addition of carbon reduced the chemical potential of boron in Si1-x-yGexCy, which deterred boron from diffusing across the underlying gate oxide.