Study of Ionization Charge Density-Induced Gain Suppression in LGADs.

M Carmen Jiménez-Ramos,Javier García López,Salvador Hidalgo,Giulio Pellegrini,Esteban Currás,Adrián García Osuna,Richard Jaramillo,Iván Vila

doi:10.3390/s22031080

Abstract

Gain suppression induced by excess carriers in Low Gain Avalanche Detectors (LGADs) has been investigated using 3 MeV protons in a nuclear microprobe. In order to modify the ionization density inside the detector, Ion Beam Induced Current (IBIC) measurements were performed at different proton beam incidence angles between 0° and 85°. The experimental results have been analyzed as a function of the ionization density projected on the multiplication layer, finding that the increase of ionization density leads to greater gain suppression. For bias voltages close to the gain onset value, this decrease in gain results into a significant distortion of the transient current waveforms measured by the Time-Resolved IBIC (TRIBIC) technique due to a deficit in the secondary holes component. For angles of incidence such that the Bragg peak falls within the sensitive volume of the detector, the formation of microplasmas modifies the behavior of the gain curves, producing an abrupt decrease in gain as the angle increases.

Highlights

Della CorteLow Gain Avalanche Detectors (LGADs) are n+ -on-p silicon sensors with intrinsic gain [1]
This technology has been developed in the framework of the RD50 Collaboration [2] and is based on the standard Avalanche Photo Diodes (APD)
The gain values presented by LGADs are moderate (10–50), without breakdown, and increase smoothly with the applied voltage when the sensor is reverse biased

Summary

Introduction

Low Gain Avalanche Detectors (LGADs) are n+ -on-p silicon sensors with intrinsic gain [1]. The gain values presented by LGADs are moderate (10–50), without breakdown, and increase smoothly with the applied voltage when the sensor is reverse biased (working in linear mode before breakdown). These gains need not be as high as those of APD detectors (usually with gain values >100, working in Geiger mode after breakdown) because, for measuring high-energy charged particles, it is not a requirement to have such high signal amplifications as for measuring low energy signals, which is a typical application of APD detectors

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