Detection enhancement in Ge-based single photon avalanche diodes

In this project, I aim to develop Single Photon Avalanche Diodes (SPADs) that are capable of highly sensitive 3D imaging, with potential applications in healthcare, autonomous vehicles, and security. SPADs are specialized devices designed to detect and precisely time the arrival of individual photons, making them crucial for a wide range of technologies, including LIDAR systems for autonomous vehicles, imaging through obscurants like fog or smoke, remote sensing of greenhouse gases, and various quantum technologies such as quantum-enhanced imaging, quantum-key distribution, and quantum computing.

The work aligns strongly to newly announced UK Quantum Hubs, particularly the Quantum Enabled Position Navigation and Timing hub. The focus of my research will be on advancing SPAD technology in the short-wave infrared (SWIR) spectral region, where current state-of-the-art devices are not only prohibitively expensive but also suffer from significant limitations such as after-pulsing, which restricts their repetition rates.

This project leverages Group IV semiconductor materials to develop SPADs that are both cost-effective and compatible with standard silicon foundries, such as those used in CMOS electronics. I will fabricate novel device SPAD geometries in the James Watt Nanofabrication Centre and characterise devices in optical laboratories. A major focus of my PhD will be to enhance SPAD performance through the integration of photonic crystals (PCs)-periodic structures designed to trap photons and increase absorption, thereby

improving the single photon detection efficiency of the devices. The work will involve experimental analysis of the design trade-offs between enhanced absorption, and the potentially detrimental effects of etching PCs into the active area on the device darkcount rate (DCR). Furthermore, I will investigate other methods of enhancing absorption with group IV alloys and band structure engineering, techniques that are also applicable

to next generation avalanche photodiodes (APDs).