Differently processed thin film transistors (TFTs) were exposed to gamma irradiation to the total dose of 1200 Gy under positive gate bias and 2500 Gy without electrical bias during radiation. Post-irradiation stability was evaluated by positive bias temperature (PBT) test in the temperature range between 100 and 150 degrees C and compared to the positive bias temperature test instability (PBTI) of non-irradiated TFTs. It was found that post-irradiation PBTI is affected by the fabrication conditions of TFTs and the level of damage caused by irradiation. (C) 2014 Elsevier B.V. All rights reserved.