Boron Ion Interaction with pnp Bipolar Power Transistor and Displacement Damage Effects on its Electrical Characteristics

Abstract

Bipolar junction transistors used in switching and amplification applications is examined for their electrical performance after irradiation with 60 MeV boron ions of different fluence. Unirradiated device base current is 5.97×10-5 A while it is 9.03×10-4 A after irradiation with a fluence of 1×1012 ions/cm2. For unirradiated device collector current is 1.22×10-3 A and is 7.31×10-4 A after irradiation to a fluence of 1×1012 ions/cm2. Base current increases whereas collector current decreases after irradiation with a fluence of 1×1012 ions/cm2. The magnitude of decrease in collector current is approximately same as that of the increase in base current, showing the leakage of the collector current due to irradiation. The output collector gain of the unirradiated transistor is 20.5 after irradiation to a fluence of 1×1012 ions/cm2 it has reduced to 0.81. The capacitance measurements for base-emitter junction show that for the unirradiated and irradiated samples, linearity of the curves indicate uniformity of shallow doping concentration. The built in potential (Vbi) for unirradiated device is 2.69V and after irradiation it is 2.52V. The device is also studied for activation energy, trap concentration and capture cross-section of deep levels are studied using deep-level transient spectroscopy (DLTS) technique. Majority carrier trap level is observed with energy Ev+0.784eV.