Active gating as a method to inhibit the crosstalk of single photon avalanche diodes in a shared well

Abstract

Advances in SPAD arrays propose improving the fill factor by confining several SPADs in the same well, with a main issue related to crosstalk. For measurements triggered only in well-defined time periods that can be known in advance, the pixels can be inhibited before the arrival of the crosstalk charge. This paper reports the crosstalk characterization of in an array of SPADs fabricated in a conventional CMOS technology in the same n-well (fill factor 67%). A long gating time gives a crosstalk not less than 2.75%, while reducing it below 2.5 ns completely eliminates crosstalk, as predicted by the theory and by TCAD simulations.

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

“…The measurements showed a crosstalk distribution with an FWHM of ~250 ps corresponding to the combined jitter of the emitter and detector, indicating the non-existence of electrical crosstalk in the given structure with the center-to-center distance between the two measured devices exceeding 100 µm. In [11,19], Vila et al performed dark noise-generated coincidence crosstalk measurements on a very dense (67% fill factor) 5 × 1 CMOS SPAD array, counting crosstalk coincidences in minimum-2.5 ns time windows. The result emphasized the importance of the electrical crosstalk in structures with small spacing between SPADs.…”

“…Although studies and experiments have been performed on crosstalk probability and its dependence on various parameters (distance between two devices, excess voltage, die thickness, etc [9, [11][12][13][14][15][16][17][18]. ), temporal correlation of the crosstalk coincidences in SPAD arrays has not been discussed extensively or has been reported with limited timing resolutions [11,12,17,19,20] (a more detailed review is presented in the Discussion section).…”