Separation of Interface Traps and Oxide Charge in Ionization Damaged Silicon Bipolar Transistors Based on Experimental Observation

An experimental concept of separating oxide-trapped charge and interface traps in silicon bipolar junction transistors (BJTs) irradiated by Co60 gamma ray is demonstrated. This concept is based on deep-level transient spectroscopy (DLTS) measurements with various filling pulsewidths. The characteristics of oxide-trapped charge and interface traps in bipolar transistors can be obtained by DLTS. The oxide-trapped charge shows positive and negative signals in the collector of NPN and PNP BJTs in DLTS signals, respectively. Unlike the oxide-trapped charge, the interface traps give positive signals in the same region of NPN and PNP BJTs.