Radiation Hardness of Modern Photogate Pixels Under Total Ionizing Dose: Impact of Pixel Pitch and Electron or Hole Collection

Gamma and X-ray irradiation results are reported on several variants of deep-trench photogate research and development pixels from STMicroelectronics. Dark current performances are compared for electron and hole-collecting pixels (n, p-type) of 2 and 1~{\mu } m pitch. Total ionizing dose (TID) results on 2~{\mu } m p-type photogates are generally consistent with previous studies, showing state-of-the-art radiation tolerance at 70 kGy (Si); 1~{\mu } m n-type pixels are found to quickly degrade under radiation, in line with expectations; 1~{\mu } m p-type photogates exhibit very promising radiation hardness, improving on the 2~{\mu } m p-type results by more than two orders of magnitude, with a dark current below 50 h+/s after 40 kGy gamma rays or 64 kGy (Si) X-rays.