Study of ionization charge density-induced gain suppression in LGADs

This article belongs to the Section Physical Sensors.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.This research was funded by the Spanish Ministry of Science, Innovation and Universities grant numbers RTI2018-098117-B-C21 and MCIN/AEI/10.13039/501100011033, the Spanish Ministry of Science, Innovation and Universities/FEDER funds grant numbers ICTS-2020-02-US-4, the Regional Ministry of Economy, Knowledge, Business and University grant number US-1380791 and the European Union’s ERDF program “A Way of making Europe” grant numbers FPA2017-85155-C4-1-R, FPA2017-85155-C4-2-R.Peer reviewe