Radiation resistant LGAD design.

In this paper, we report on the radiation resistanceof 50-micron thick LGAD detectors manufactured at the Fondazione Bruno Kessler employing several different doping combinations of the gain layer. LGAD detectors with gain layer doping of Boron, Boronlow-diffusion, Gallium, Carbonated Boronand Carbonated Galliumhave been designed and successfully produced. These sensors have been exposed to neutron fluences up to $\phi_n \sim 3 \cdot 10^{16}\; n/cm^2$ and to proton fluences up to $\phi_p \sim 9\cdot10^{15}\; p/cm^2$ to test their radiation resistance. The experimental results show that Gallium-doped LGADs are more heavily affected by initial acceptorremoval than Boron-doped LGAD, while the presence of Carbon reduces initial acceptorremoval both for Galliumand Borondoping. Boronlow-diffusion shows a higher radiation resistancethan that of standard Boronimplant, indicating a dependence of the initial acceptorremoval mechanism upon the implant width. This study also demonstrates that proton irradiation is at least twice more effective in producing initial acceptorremoval, making proton irradiation far more damaging than neutron irradiation.