Development of Heterogeneously Integrated Photodiodes on Silicon Nitride, Segmented Waveguide Photodiodes, and Zero-Bias Photodiodes

Photodiodes are being used in numerous applications nowadays. Depending on their use, photodiodes require various designs and optimization goals. In my work, I focus on photodiode developments for silicon photonics, integrated quantum optics, and microwave photonics. My work includes design, fabrication, and characterization of different structures based on these applications’ requirements.
Starting with silicon photonics, I have developed a new die bonding process based on a very thin adhesive layer (SU-8). This technique enabled designs to achieve high-performance waveguide photodiodes on a silicon photonics platform. Using this technique, I developed record-high responsivity PIN photodiodes on silicon nitride waveguides. By further optimizing the epitaxial layer structure, the bonding, and the fabrication process, I was able to demonstrate a waveguide photodiode with 20 GHz bandwidth and even higher responsivity. Low dark current and a record-high quantum efficiency were achieved in single and balanced photodiodes. These photodiodes are promising candidates for high-speed Si3N4 photonic integrated circuit applications.
For integrated quantum optics, I developed a novel segmented waveguide photodetector based on a directional coupler design. By matching the imaginary parts of the propagation constants of the even and odd modes in the design, an integrated optical detector with near-unity quantum efficiency is achieved. This work represents a new approach for integrated photon number resolving (PNR) detectors.
Finally, bias-free photodiodes are required to reduce the power consumption and electrical cross-talk in data center applications. I demonstrated a bias-free photodiode with 40 GHz bandwidth and a record-high output power.