Single-photon avalanche diodes in 0.18-μm high-voltage CMOS technology

Design and simulation of a near-infrared enhanced Si-based SPAD for an automotive LiDAR

A near-infrared (NIR)-enhanced single-photon avalanche diode (SPAD) with a retrograded NM/XP junction for an automotive LiDAR was designed based on CSMC 0.18 µm BCD technology. A 3 µm depth NM/XP junction embedded in a lightly doped deep p-well (DP) improves the absorption efficiency in the NIR regime; the photo-generated electrons generated in the depletion region are efficiently collected into the central multiplication region by a drift process, and then the impact ionization is triggered by the strong field, resulting in a high photon detection efficiency (PDE). Additionally, the deep NM/XP junction and the buried layer effectively isolate the dark noise originating from the interface and the substrate. The SPAD was initially simulated by numerical calculation, and then was evaluated with active quench/reset electronics in a circuit simulator. The results revealed that the SPAD with an active area of 314µm 2 achieves a PDE of 16.2% at 905 nm and a dark count rate (DCR) of 1.46H z/µm 2, with an excess bias of 5 V at room temperature. The designed SPAD is well suited for the low-cost, miniaturized automotive LiDAR.

Photon-Detection-Probability Simulation Method for CMOS Single-Photon Avalanche Diodes

Single-photon avalanche diodes (SPADs) in complementary metal-oxide-semiconductor (CMOS) technology have excellent timing resolution and are capable to detect single photons. The most important indicator for its sensitivity, photon-detection probability (PDP), defines the probability of a successful detection for a single incident photon. To optimize PDP is a cost- and time-consuming task due to the complicated and expensive CMOS process. In this work, we have developed a simulation procedure to predict the PDP without any fitting parameter. With the given process parameters, our method combines the process, the electrical, and the optical simulations in commercially available software and the calculation of breakdown trigger probability. The simulation results have been compared with the experimental data conducted in an 800-nm CMOS technology and obtained a good consistence at the wavelength longer than 600 nm. The possible reasons for the disagreement at the short wavelength have been discussed. Our work provides an effective way to optimize the PDP of a SPAD prior to its fabrication.