Charge trapping and recombination in dipolar field of charged defect cluster in silicon

TL;DR

This paper investigates how internal electric fields from defect clusters in irradiated silicon influence charge recombination and lifetime, highlighting the role of charge diffusion length relative to cluster size.

Contribution

It introduces a model including drift and diffusion to analyze how dipolar defect clusters affect charge recombination in silicon sensors.

Findings

Charge diffusion length comparable to cluster size significantly increases recombination.

Large internal electric fields from defect clusters can reduce charge lifetime.

Effect diminishes when diffusion length exceeds cluster dimensions.

Abstract

Extensive irradiation of silicon crystal sensors by high energy particles in e. g. accelerators yield defect clusters of different types. Trapping of electrons and holes result in extended internal electric fields that drive remaining free charges. The question whether these internal electric fields affect the experimental observables, e.g. recombination process and lifetime of free charges is the main focus of this paper. Including the drift and diffusion of electrons and holes we calculate the recombination rate in a cubic sample with a single dipolar cluster of defects. It is shown that the large effect on charge lifetime is to be expected when charge diffusion length during the charge lifetime is comparable to the dimensions of the cluster. If the diffusion length exceeds the cluster size, the cluster barely affects the recombination rate.