Modeling-Based Optimization of a Single-Photon Avalanche Diode: Towards Integrated Quantum Photonics Devices Operating at Room-Temperature

Single-photon avalanche diodes (SPADs) are emerging as a cost-effective and practical alternative to superconducting nanowire single-photon detectors (SNSPDs), especially for integrated quantum photonics. While SNSPDs exhibit excellent performance such as fast response time and high detection efficiency, their reliance on a cryogenic cooling system results in high cost and power consumption as well as limited suitability for portable devices. In contrast, SPADs can operate at room temperature, eliminating the need for a bulky cooling system and significantly reducing the overall cost. Compared to SNSPDs, however, further optimization of SPAD performance is highly required. In this paper, the SPAD guard-ring (GR) structure is optimized with accurate SPAD device modeling and TCAD simulation, aiming to enhance their suitability for integrated quantum photonics applications. It is demonstrated that the GR-optimized SPAD can reduce internal series resistance and extend its avalanche multiplication region. As a result, the avalanche multiplication region is expanded by approximately 20%, and the peak photon detection probability at a wavelength of 425 nm is increased by 48% . This improvement is achieved while maintaining a low dark count rate of 3.9 cps/μm² at an excess bias voltage of 3 V. Additionally, the reduced series resistance enables an increase in current gain and a faster slew rate, which results in much lower timing jitter.