Optical studies of infrared active electronic defects in neutron irradiated silicon after annealing at 450 C

Using Fourier transform infrared absorption spectroscopy and Hall effect measurements mainly the infrared active electronic defects in fast neutron irradiated float-zone silicon and Czochralski silicon after annealing at 450 C are investigated. Introducing thermal donors (TD) to alter the Fermi level, the defect associated with the higher-order bands (HOB) is analyzed, which is proposed to have at least three charge states within the band gap. The defect level giving rise to the HOB is located slightly below Ec -0.15 eV, and another level possibly exists near the bottom of the conduction band. Moreover, the measurement results indicate that the characteristic of photoexcitation and decay of the HOB is associated with the slow relaxation process of photoexcited carriers. (orig.)