Improving performance of single-photon avalanche diodes for quantum photonics application

This paper examines a new structure of Single Photon Avalanche Diodes (SPADs) incorporating surface fields to improve the device’s performance. We developed a physics-based TCAD model to simulate the performance of the new SPAD devices. The model implements an n-well p-sub junction SPAD with a surface field over the junction and includes all features of an SPAD fabricated in a standard CMOS process. We investigated the device’s electric field, space charge distribution, and breakdown voltage. The surface field modulates the electric field around the junction, making it more uniform which prevents premature edge breakdown. The applied surface field also modulates the breakdown voltage. Since the performance of the SPAD devices depends on the breakdown voltage, the device performance, including noise, sensitivity can be improved by the surface field. Preliminary simulations demonstrate the potential of new SPAD devices with external surface fields for applications such as quantum computing.