Radiation Hardness of Thin Low Gain Avalanche Detectors

Abstract

Low Gain Avalanche Detectors (LGAD) are based on a n++-p+-p-p++ structure where an appropriate doping of the multiplication layer (p+) leads to high enough electric fields for impact ionization. Gain factors of few tens in charge significantly improve the resolution of timing measurements, particularly for thin detectors, where the timing performance was shown to be limited by Landau fluctuations. The main obstacle for their operation is the decrease of gain with irradiation, attributed to effective acceptor removal in the gain layer. Sets of thin sensors were produced by two different producers on different substrates, with different gain layer doping profiles and thicknesses (45, 50 and 80 um). Their performance in terms of gain/collected charge and leakage current was compared before and after irradiation with neutrons and pions up to the equivalent fluences of 5e15 cm-2. Transient Current Technique and charge collection measurements with LHC speed electronics were employed to characterize the detectors. The thin LGAD sensors were shown to perform much better than sensors of standard thickness (~300 um) and offer larger charge collection with respect to detectors without gain layer for fluences <2e15 cm-2. Larger initial gain prolongs the beneficial performance of LGADs. Pions were found to be more damaging than neutrons at the same equivalent fluence, while no significant difference was found between different producers. At very high fluences and bias voltages the gain appears due to deep acceptors in the bulk, hence also in thin standard detectors.

References in corpus (5)

• Beam test results of a 16 ps timing system based on ultra-fast silicon detectors
• Properties of a radiation-induced charge multiplication region in epitaxial silicon diodes
• Neutron irradiation test of depleted CMOS pixel detector prototypes
• Gain and time resolution of 45 $\mu$m thin Low Gain Avalanche Detectors before and after irradiation up to a fluence of $10^{15}$ n${}_{eq}$/cm${}^2$
• Trapping in irradiated p-on-n silicon sensors at fluences anticipated at the HL-LHC outer tracker

Cited by in corpus (13)

• Radiation resistant LGAD design
• Timing performance of small cell 3D silicon detectors
• First FBK Production of 50$\mu$m Ultra-Fast Silicon Detectors
• Beam test measurements of Low Gain Avalanche Detector single pads and arrays for the ATLAS High Granularity Timing Detector
• Radiation Campaign of HPK Prototype LGAD sensors for the High-Granularity Timing Detector (HGTD)
• Low Gain Avalanche Detectors for the HADES reaction time (T${}_0$) detector upgrade
• Beam test results of IHEP-NDL Low Gain Avalanche Detectors(LGAD)
• The performance of large-pitch AC-LGAD with different N+ dose
• Leakage current simulations of Low Gain Avalanche Diode with improved Radiation Damage Modeling
• The performance of IHEP-NDL LGAD sensors after neutron irradiation
• Fabrication of a Silicon Electron Multiplier sensor using Metal Assisted Chemical Etching and its characterisation
• Annealing effects on operation of thin Low Gain Avalanche Detectors
• Impact of Neutron Irradiation on LGADs with a Carbon-Enriched Shallow Multiplication Layer: Degradation of Timing Performance and Gain