Afterpulse-like noise limits dynamic range in time-gated applications of thin-junction silicon single-photon avalanche diode

Abstract

We describe a source of noise in thin-junction silicon single-photon avalanche diode arising after strong illumination either during the ON (voltage above breakdown) or the OFF (voltage below breakdown) time. It increases the background noise with respect to primary dark count rate similarly to the afterpulsing process, but it is not related to a previous detector ignition. The amount of noise is linearly dependent on the power of light impinging on the detector and time constants are independent of the electric field. This phenomenon is the main limiting factor for the dynamic-range during time-gated measurements in condition of strong illumination

Memory effect in silicon time-gated single-photon avalanche diodes

“…13, we demonstrated that the difference in background decays collected within the second window by switching between the DGC and the SGC is only due to the afterpulsing contribution, which is dominant only in the DGC. Indeed, in the presence of the first gate window, the avalanche can self-sustain and so the number of carriers within the junction is orders of magnitude higher than in SGC, thus boosting the trapping process.…”

“…1), we demonstrated: 13 (i) ME is generated when the detector is exposed to a strong illumination and linearly increases with the number of incoming photons; (ii) ME decays with time constants longer than those ascribed to classical afterpulsing processes in silicon SPADs; (iii) ME has decay time constants not sensitive to the electric field applied to the junction; (iv) differently from classical afterpulsing, ME arises even if the detector is kept OFF during the illumination phase, by lowering the reverse voltage below breakdown (thus quite inhibiting any charge carrier multiplication within the depletion region). Considering all these findings, we speculated that ME is not due to carrier trapping within the depleted region, but it can arise from a physical process occurring outside it, where the electric field is negligible.…”

“…On the other hand, it highlighted an unknown source of background noise in thin-junction silicon SPADs, due to a sort of "memory effect" (ME), whose discovery and preliminary characterization we reported in Ref. 13. This effect causes the noise avalanche ignitions to be not uniformly distributed within the time-gated window, thus resulting in a background therein that is decaying instead of being flat.…”

“…This process is similar to what happens in linear-mode avalanche photodiodes. Instead ME in silicon SPADs cannot be ascribed to a similar kind of trapping since the decaying time constants are much longer than those of afterpulsing and they do not depend on the electric field, 13 as it might a)…”

Characterization of a time-resolved non-contact scanning diffuse optical imaging system exploiting fast-gated single-photon avalanche diode detection

“…Its value was obtained in an initial measurement without clipping the curve by the gate. An additional background component due to the "memory effect" 26,31 is related to the total amount of light impinging on the detector when it is off and thus increases with increasing delay. Therefore it cannot be subtracted as a constant background but should remain part…”