Characteristics of displacement defects in PNP transistors caused by heavy ion irradiation

Characteristics of displacement defects in the 3CK3637 PNP bipolar junction transistors (BJTs) irradiated by 10 MeV Si, 40 MeV Si and 25 MeV C ions are investigated in this paper. Electrical parameters are measured in-situ using KEITHLEY a 4200-SCS semiconductor characterization system during irradiations. The radiation-induced defects caused by various ions for different displacement damage doses are characterized by deep level transient spectroscopy (DLTS). Experimental results show that the electrical degradation increases with increasing irradiation fluence. It is worth noting that the increase trend of the electrical degradation is different for the three types of ions. For the 10 MeV Si ions, the electrical degradation linearly increases, while, for the 40 MeV Si and 25 MeV C ions, the electrical degradation increases nonlinearly. The change in the reciprocal of current gain (Δ(1/β)) caused by 40 MeV Si and 25 MeV C ions can be normalized in one line at lower displacement damage doses. As the displacement damage dose increases to a certain threshold, the Δ(1/β) deviates from the normalized line. Based on the DLTS analyses, the dominant displacement defects in the 3CK3637 PNP BJTs irradiated by 40 MeV Si and 25 MeV C ions change with increasing displacement dose, leading to the existence of threshold in the electrical degradation curve.