Characterization and modeling of crosstalk and afterpulsing in Hamamatsu silicon photomultipliers

TL;DR

This paper thoroughly investigates the sources and characteristics of crosstalk and afterpulsing in Hamamatsu silicon photomultipliers, proposing models and design improvements to reduce these noise components.

Contribution

It provides a detailed characterization of correlated noise in MPPCs, introduces a Monte Carlo simulation, and suggests design modifications to mitigate crosstalk and afterpulsing.

Findings

Prompt crosstalk is mainly due to secondary photons and reflected light.

Increasing substrate doping density reduces afterpulsing and delayed crosstalk.

Longer trenches could significantly decrease crosstalk in MPPCs.

Abstract

The crosstalk and afterpulsing in Hamamatsu silicon photomultipliers, called Multi-Pixel Photon Counters (MPPCs), have been studied in depth. Several components of the correlated noise have been identified according to their different possible causes and their effects on the signal. In particular, we have distinguished between prompt and delayed crosstalk as well as between trap-assisted and hole-induced afterpulsing. The prompt crosstalk has been characterized through the pulse amplitude spectrum measured at dark conditions. The newest MPPC series, which incorporate isolating trenches between pixels, exhibit a very low prompt crosstalk, but a small component remains likely due to secondary photons reflected on the top surface of the device and photon-generated minority carriers diffusing in the silicon substrate. We present a meticulous procedure to characterize the afterpulsing and delayed crosstalk through the amplitude and delay time distributions of secondary pulses. Our results indicate that both noise components are due to minority carriers diffusing in the substrate and that this effect is drastically reduced in the new MPPC series as a consequence of an increase of one order of magnitude in the doping density of the substrate. Finally, we have developed a Monte Carlo simulation to study the different components of the afterpulsing and crosstalk. The simulation results support our interpretation of the experimental data. They also demonstrate that trenches longer than those employed in the Hamamatsu MPPCs would reduce the crosstalk to a much greater extent.