Bipolar Phototransistors Reliability Assessment for Space Applications

Life test, total dose and proton irradiations were performed on silicon-based bipolar phototransistors. A high radiation sensitivity was observed together with abnormal fluctuations of phototransistors collector current during life test. In an attempt to solve this problem, a failure analysis was conducted. Mobile charges located in the photobase passivation layer were found to be at the origin of these fluctuations and are probably also related to the high radiation sensitivity of these devices. Based on the obtained results a new device selection method for space application is proposed.