Timing and probability of crosstalk in a dense CMOS SPAD array in pulsed TOF applications

Area of Science:

• Photonics and Semiconductor Devices
• Integrated Circuits and Systems

Background:

• Increasing density in CMOS single-photon avalanche diode (SPAD) arrays leads to significant crosstalk.
• Crosstalk limits the fill factor and performance of SPAD arrays.

Purpose of the Study:

• Investigate temporal correlation, probability, and influencing parameters of crosstalk in CMOS SPAD arrays.
• Characterize crosstalk dependence on illumination, distance, and device parameters.

Main Methods:

• Measurement of a ~45%-fill factor CMOS SPAD array using 0.35-µm HV CMOS technology.
• Utilized on-chip time-to-digital converters (65-ps resolution) for coincidence measurements.
• Induced crosstalk using internal SPAD noise and analyzed pulsed time-of-flight measurements.

Main Results:

• Observed both optical and electrical crosstalk with distinct temporal distributions.
• Measured crosstalk probabilities of 0.3% and 0.01% for adjacent pixels (FWHM 700 ps and 400 ps).
• Pulsed illumination significantly increased correlated noise due to substrate photon absorption.

Conclusions:

• Crosstalk is a critical factor affecting SPAD array density and performance.
• Understanding temporal crosstalk characteristics is essential for mitigating noise.
• Substrate effects play a role in crosstalk, particularly under pulsed illumination.