The Ge-on-Si integrated microphotonic platform

During the past twenty-five years hetero-epitaxial structures of germanium on silicon have played three essential roles: i) a tool for the study of interface coherency at lattice misfit interfaces; ii) a basis for strain-scaling of channel mobility in silicon transistors; and iii) a foundation for monolithic integration of active photonic devices in silicon microphotonics. Coherency and strained silicon employ Ge as a minority constituent in SiGe alloys, while Ge microphotonic devices are comprised of near 100% Ge. The three topics share a common learning curve that has had major impact on information technology.