On the correlation between high-order bands and some photoluminescence lines in neutron-irradiated FZ silicon

The defects in float-zone silicon irradiated by fast neutron with fluences up to 4.0×1018 n/cm2, followed by various heat treatments, have been studied by low-temperature photoluminescence (PL) and infrared absorption measurement with emphasis upon the high-order band (HOB) and its relationship with the commonly observed PL-lines such as I1 (1.018 eV) and I3(1.039 eV). It has been shown that band 1124 cm−1, unlike the other higher-order bands, is considerably broader for the sample annealed at low temperature (for example, 385 °C) with FWHM as large as 3 meV and is apparently narrowed as the anneal temperature was increased. We have obtained the I3 line and its phonon replicas in the near-infrared absorption measurement, further proving the transition involved in the I3 defect center to be electronic in nature. The combination of luminescence and absorption experiment results demonstrated that the HOB could be well developed after PL lines such as I1 and I3 disappeared completely, or vice versa. PL lines could be observed before the HOB emerged, therefore ruling out the possibility proposed by earlier authors that the HOB could be correlated with some PL lines.