Crosstalk-Free Single Photon Avalanche Photodiodes ... - IEEE Xplore

IEEE ELECTRON DEVICE LETTERS, VOL. 35, NO. 1, JANUARY 2014

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Crosstalk-Free Single Photon Avalanche Photodiodes Located in a Shared Well Anna Vilà, Eva Vilella, Oscar Alonso, and Angel Dieguez, Member, IEEE

Abstract— Advances in single photon avalanche detector (SPAD) arrays propose improving the fill factor by confining several SPADs in the same well, with a main issue related to crosstalk. In applications that measure at fixed times, the pixels can be inhibited before the arrival of the crosstalk charge. This letter reports the crosstalk characterization in an array of SPADs, where the sensors share the same n-well (fill factor 67%), and fabricated in a conventional CMOS technology. The reduction of the gating time 1 ns [11]. Presumably, the slope of the curve in figure 3 is related to the position distribution in which the avalanches are generated. The experiment agrees with the previous theoretical results, demonstrating the possibility to eliminate crosstalk by means of the time-gated operation of the SPAD with tobs shorter than 2.5 ns. Consequently, the dynamic range (ratio between maximum and minimum detectable intensities) can be extended. To be sure that coincidences are only due to crosstalk, it has been verified there are no additional contributions due just to random simultaneity of dark counts. To do that, a photodiode with a high sensitivity (large Dark Count Rate, DCR) in a relatively quiet environment offers the ideal situation [10]. So, pixel 1 (with a DCR of 42.48 kHz, between pixel 0,

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