Doppler broadening of positron annihilation on gamma, neutron, and electron-irradiated N- and P-type Silicon wafers

In this research, Doppler broadening measurements of positron annihilation have been done on N- and P-type irradiated silicon wafers which have widely used in the electronics industry. The wafers were irradiated by 10-MeV electrons beam (30 kGy), 60Co gamma rays (175 kG) and thermal neutrons (~ 0.038 Gy). The radioactive isotope of 22Na with an activity of about 7µCi, which is enclosed between two thin polymer layers with a thickness of 7µm were used as a positron source. A conventional setup using an HPGe semiconductor detector in coincidence with a NaI(Tl) scintillator detector. The results of this research indicate the presence of visible defects in the electron irradiated samples.