Inter-pad dead regions of irradiated FBK Low Gain Avalanche Detectors

TL;DR

This paper investigates the effects of neutron irradiation on the inter-pad dead regions of FBK Low Gain Avalanche Detectors, revealing how radiation damage influences the insensitivity zones and their alignment with nominal specifications.

Contribution

It provides the first detailed measurement of how neutron radiation affects the inter-pad dead zones in LGADs, using a TCT laser system and beta particles for characterization.

Findings

Higher neutron fluence improves the match between measured and nominal IPDs.

Neutron damage alters the size of dead zones, affecting detector performance.

The study offers insights into radiation effects on LGADs for high-radiation environments.

Abstract

Low Gain Avalanche Detectors (LGADs) are a type of thin silicon detector with a highly doped gain layer. LGADs manufactured by Fondazione Bruno Kessler (FBK) were tested before and after irradiation with neutrons. In this study, the Inter-pad distances (IPDs), defined as the width of the distances between pads, were measured with a TCT laser system. The response of the laser was tuned using $\beta$-particles from a 90Sr source. These insensitive "dead zones" are created by a protection structure to avoid breakdown, the Junction Termination Extension (JTE), which separates the pads. The effect of neutron radiation damage at \fluence{1.5}{15}, and \fluence{2.5}{15} on IPDs was studied. These distances are compared to the nominal distances given from the vendor, it was found that the higher fluence corresponds to a better matching of the nominal IPD.