Characterization of Radiation Defect Centers in Neutron Irradiated Si Using Inverse Laplace Transformation to Analysis of Photocurrent Relaxation Waveforms

High-resolution photoinduced transient spectroscopy has been applied to investigating the effect of the 1 MeV neutron fluence on the electronic properties of radiation defects in Czochralski grown silicon in magnetic field. A new approach to the analysis of the photocurrent relaxation waveforms as a function of time and temperature has been presented. It is based on using a two-dimensional numerical procedure with implementation of the inverse Laplace transformation for creating images of the sharp spectral fringes depicting the temperature dependences of the thermal emission rate for detected defect centers. In the material irradiated with the fluence of 3×$10^{14} cm^{-2}$, the dominant traps with activation energies of 75 meV and 545 meV are tentatively identified with an aggregate of three Si interstitials and the trivacancy, respectively. In the material irradiated with the fluence by the order of magnitude higher, the activation energies of the main traps are found to be 115, 350, 505, 545, and 590 meV. These traps are tentatively attributed to an aggregate of four Si interstitials, as well as to vacancy related centers such as $V_3$ (2-/-), $V_2O$ (-/0), $V_3$ (-/0) and $V_4$ (-/0), respectively.