Radiation Campaign of HPK Prototype LGAD sensors for the High-Granularity Timing Detector (HGTD)

We report on the results of a radiation campaign with neutrons, protons and gammas of Low-Gain Avalanche Detectors (LGAD) produced by HPK as prototypes for the HGTD in ATLAS. With a common mask, sensors with an active thickness of 50 µm (2 splits) and 35 µm (3 splits) were produced. The different splits refer to different combinations of the doping profile of the gain layer and the resistivity of the bulk. Sensors were irradiated separately in steps of roughly 2x up to a fluence of 3E15 neq/cm2. As a function of the fluence, the following results will be reported for operation at -30C: the power and breakdown voltage using I-V measurement, doping profile for the gain layer and the bulk from C-V data, and the collected charge and time resolution from measurements with laser and charged particles. The results will be compared to the goal of operating the HGTD efficiently up to a fluence of 3E15 neq/cm2.