The properties of 50 μm thick Low Gain Avalanche Diode (LGAD) detectors manufactured by Hamamatsu photonics (HPK) and Fondazione Bruno Kessler (FBK) were tested before and after irradiation with neutrons. Their performance were measured in charge collection studies using β-particles from a 90Sr source and in capacitance-voltage scans (C-V) to determine the bias to deplete the gain layer. Carbon infusion to the gain layer of the sensors was tested by FBK in the UFSD3 production. HPK instead produced LGADs with a very thin, highly doped and deep multiplication layer. The sensors were exposed to a 1 MeV neutron equivalent (neq/cm2) neutron fluence from 4× 1014 neq/cm2 to 4× 1015 neq/cm2. The collected charge and the timing resolution were measured as a function of bias voltage at −30 C, furthermore the profile of the capacitance over voltage of the sensors was measured. The deep gain layer (HPK-3.2) and the Carbon infusion (FBK3+C) both show reasonable performance up to 3× 1015 neq/cm2. Furthermore the correlation between the time resolution and the gain is found to be independent from the sensor type, given the same thickness, and from the fluence. Finally a correlation is shown between the bias voltage to deplete the gain layer and the bias voltage needed to reach a certain amount of gain in the sensor.

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This paper studied the radiation hardness of low gain avalanche detector (LGAD) developed by the Novel Device Laboratory (NDL) in Beijing and the Institute of High Energy Physics (IHEP) of Chinese Academy of Sciences, in the context of an upgrade project of the ATLAS detector for the high luminosity phase of LHC. NDL LGAD sensors with di↵erent layouts, epitaxial resistivity, doping profile were irradiated up to 1.02 ⇥10 15 n eq /cm 2 by 70 MeV proton at Cyclotron and Radioisotope Center (CYRIC). The timing resolution of NDL LGAD sensors reached 50 picoseconds (ps) and the collected charge reached 3-4 Femtocoulombs (fC) after irradiation.