Abstract
Being ready-to-detect over a certain portion of time makes the time-gated single-photon avalanche diode (SPAD) an attractive candidate for low-noise photon-counting applications. A careful SPAD noise and performance characterization, however, is critical to avoid time-consuming experimental optimization and redesign iterations for such applications. Here, we present an extensive empirical study of the breakdown voltage, as well as the dark-count and afterpulsing noise mechanisms for a fully integrated time-gated SPAD detector in 0.35-m CMOS based on experimental data acquired in a dark condition. An “effective” SPAD breakdown voltage is introduced to enable efficient characterization and modeling of the dark-count and afterpulsing probabilities with respect to the excess bias voltage and the gating duration time. The presented breakdown and noise models will allow for accurate modeling and optimization of SPAD-based detector designs, where the SPAD noise can impose severe trade-offs with speed and sensitivity as is shown via an example.
Highlights
CMOS realization in array format and high sensitivity in the visible and near-infrared spectral range have made the single-photon avalanche diode (SPAD) a very attractive low-light detector for different sensor and imaging applications such as laser ranging, quantum processing, biomedical microscopy, astronomical telescopes, optical communication, etc. [1,2,3,4,5,6,7]
When the SPAD is operated in a free-running quench/reset mode, the released carriers can trigger afterpulse events any time after the SPAD is reset above breakdown again, and the afterpulsing probability can be reduced only by increasing the quencher dead-time, which may not be a good solution if high speed is a requirement
We proposed to use the same measurement data to characterize afterpulsing defined as the chance to detect a detrapped carrier as it is irrelevant if the previous detection event has been triggered due to photon absorption or thermal generation of carries
Summary
CMOS realization in array format and high sensitivity in the visible and near-infrared spectral range have made the single-photon avalanche diode (SPAD) a very attractive low-light detector for different sensor and imaging applications such as laser ranging, quantum processing, biomedical microscopy, astronomical telescopes, optical communication, etc. [1,2,3,4,5,6,7]. The Geiger mode (digital) operation imposes other noise mechanisms, i.e., SPAD intrinsic parasitics, creating avalanche detection counts without a photon being absorbed. This includes detection counts triggered by thermally or tunneling-generated carriers (i.e., dark-count noise), as well as the counts that are strongly correlated with previous avalanche detections (so-called afterpulsing noise) [8,9]. In Mahmoudi et al [9], a statistical approach was presented to measure different SPAD noise mechanisms using experimental data acquired in a dark condition, which is the most basic and straightforward performance measurement of the SPAD This statistical approach, is only appropriate for detectors with quench/reset circuitry, where the SPAD bias is returned to above the breakdown after any detection to be ready and waiting for the detection (i.e., free-running operation).
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