University of Oulu

Sahba Jahromi and Juha Kostamovaara, "Timing and probability of crosstalk in a dense CMOS SPAD array in pulsed TOF applications," Opt. Express 26, 20622-20632 (2018)

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

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Author: Jahromi, Sahba1; Kostamovaara, Juha1
Organizations: 1University of Oulu, Faculty of Information Technology and Electrical Engineering, Circuits and Systems (CAS) Research Unit
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.9 MB)
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Language: English
Published: Optical Society of America, 2018
Publish Date: 2018-10-04


As the distance between neighboring devices in large CMOS single-photon avalanche diode (SPAD) arrays is reduced for improving the density, increased crosstalk becomes an important issue, limiting the maximum practical fill factor of the array. In this study, the temporal correlation of crosstalk events, as well as the crosstalk probability, and their dependence on parameters, such as the illumination wavelength and intensity, and the distance between SPADs, are investigated via measurement of a ~45%-fill factor CMOS SPAD array fabricated using 0.35-µm high-voltage CMOS technology. The SPADs have 24 µm × 24 µm square-shaped active areas, and all devices share a common deep-N-well cathode. On-chip time-to-digital converters with 65-ps resolution are used to measure the timing of crosstalk events in “coincidence measurements.” For the crosstalk measurements, the internal noise in one SPAD is used to produce crosstalk events in the neighboring devices. The measurement results indicate both optical and electrical crosstalk with the crosstalk events, having a specific temporal distribution. The crosstalk probability in the first two adjacent pixels is found to be 0.3% and 0.01%, with a distribution having full widths at half maximum (FWHMs) of 700 and 400 ps, respectively. In pulsed time-of-flight measurements, when one SPAD is triggered with external short-pulsed (FWHM of approximately 200 ps) illumination, extra correlated noise in the adjacent SPADs added to the crosstalk noise, increasing the correlated noise considerably. This additional noise was a secondary effect of the absorbed laser photons deep in the substrate.

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Series: Optics express
ISSN: 1094-4087
ISSN-E: 1094-4087
ISSN-L: 1094-4087
Volume: 26
Issue: 16
Pages: 20622 - 20632
DOI: 10.1364/OE.26.020622
Type of Publication: A1 Journal article – refereed
Field of Science: 213 Electronic, automation and communications engineering, electronics
Funding: Academy of Finland (Centre of Excellence in Laser Scanning Research, contract no. 307362).
Academy of Finland Grant Number: 307362
Detailed Information: 307362 (Academy of Finland Funding decision)
Copyright information: © 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.