Strained germanium-tin (GeSn) N-channel MOSFETs featuring low temperature N+/P junction formation and GeSnO2 interfacial layer

In this paper, we report the world´s first germanium-tin (GeSn) channel nMOSFETs. Highlights of process module advances are: low temperature (400 °C) process for forming high quality n+/p junction with high dopant activation and reduced dopant diffusion; interface engineering achieved with GeSnO₂ interfacial layer (IL) between high-k gate dielectric and GeSn channel. A gate-last process was employed. The GeSn nMOSFET with GeSnO₂ IL demonstrates a substantially improved SS in comparison with Ge control, and an ION/IOFF ratio of 10⁴.