Monolithic Integration of Top Si₃N₄- Waveguided Germanium Quantum-Dots Microdisk Light Emitters and PIN Photodetectors for On-chip Ultrafine Sensing

Using a coordinated combination of lithographic patterning and self-assembled growth, Ge spherical quantum-dots (QDs) were controllably generated within host Si-{3}N-{4} layers as active medium for Si photonics. A significant fabrication advantage of our approach is the high-temperature thermal stability of Ge QDs that are formed by thermal oxidation of poly-SiGe at 900{o}C, offering process flexibility in the waveguide-material choices and device designs. Our Ge QDs enable monolithic integration of mu disk light-emitters and PIN photodetectors (PDs) with top Si-{3}N-{4}/SiO2/Ge waveguide-coupled structures using standard Si processing. Over 95% coupling efficiency from SiN WGs to Ge QD PDs is achievable. Ultralow dark current of 0.1 pA/ mu m, high responsivity of 3,500 A/W at 850 nm and 10A/W at 1550 nm, 3dB frequency gt10 GHz for Ge-QD PDs and low threshold power of 0.6 kW/cm{2} for optically-pumped Ge QD/SiN mu - disks lasing evidence the high degree of crystallinity of our Ge QDs as an effective building block for 3D SiN PICs.