Degradation differences in the forward and reverse current gain of 25 MeV Si ion irradiated SiGe HBT

Abstract The silicon–germanium (SiGe) heterojunction bipolar transistors (HBTs) were exposed to 25 MeV Si ions with ion fluence from 9.1×10 8 to 4.46×10 10  ions/cm 2 at room temperature. The forward current gain ( β F ) and reverse current gain ( β R ) were studied before and after irradiation and the bias dependences of the displacement damage factor for β F and β R were also presented. Measurement results indicated that β F and β R all decline with the ion fluence increasing. The reciprocal of β R was found to vary linearly throughout all ion fluence for arbitrary base-collector voltage. However, a non-linear behavior for the reciprocal of β F appeared at low fluence for the low and medium base-emitter voltage. Besides, it was found that the bias dependence of displacement damage factor for β F was significantly different from that for β R . The underlying physical mechanisms were analyzed and investigated in detail.