Self-Organized Germanium Quantum Dots/Si3N4 Enabling Monolithic Integration of Top Si3N4-Waveguided Microdisk Light Emitters and p-i-n Photodetectors for On-Chip Sensing

Using a coordinated combination of lithographic patterning and self-assembled growth, Ge spherical quantum dots (QDs) were controllably generated within host layers of Si3N4 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 lithographically patterned structures at 800 °C–900 °C, offering flexibility in the waveguide (WG)-material choices, co- design, and integration of Ge photonic devices. Our Ge QDs enable monolithic integration of microdisk light emitters and p-i-n photodetectors (PDs) with top-Si3N4 WG-coupled structures using standard Si processing. Low dark current of 0.3 mA/cm2 at 300 K and
$0.2\,\mu \text{A}$
/cm2 at 77 K in combination with 3-dB frequency of 12 GHz for Ge-QD PDs and low threshold power of 0.6 kW/cm2 for optically pumped Ge QD/SiN microdisks light emission evidence the high degree of crystallinity of our Ge QDs being an effective building block for 3-D SiN photonic integrated circuits.