GeSn technology: Extending the Ge electronics roadmap

First principles study showed indicated band gap of Ge can be tuned by alloying with Sn and metastable GeSn alloys can be synthesized at or above room temperature. Subsequently, high quality GeSn layers were grown using low temperature MBE. PL indicated good crystal quality of GeSn material with a reduced direct bandgap. Challenges involved in CMOS processing on GeSn were addressed through effective surface cleaning and a low thermal budget process flow. To the best of our knowledge this work is the first demonstration of a high-κ pMOSFET using 3% GeSn as channel material showing 20% improvement in hole mobility compared to Ge. Alloying Ge with Sn has thus been shown as a performance booster for Ge based devices. Further improvements in material quality and incorporation of higher substitutional Sn, coupled with strain and bandgap engineering, significant performance gains can be achieved from this alloy system.