Iron-related deep levels in n-type silicon

Deep levels in iron-doped n-type silicon have been investigated by deep-level transient spectroscopy (DLTS). Three deep levels of E _c-0.29 eV (E1), E_c-0.36 eV (E2), and E_c-0.48 eV (E3) were observed. The concentration of E1 and E2 levels increased during the storage at room temperature. The depth profile of the E3 level concentration indicates the out-diffusion and precipitation of the defects related to the E3 level. In addition, after annealing at 80 °C for 30 min, the E2 and E3 concentrations decreased and then recovered at room temperature. These results suggest that the defects related to these levels are mobile during quenching and storage at room temperature. The temperature dependence of the E3 level concentration shows a formation energy of about 2 eV, which is smaller than that of interstitial iron, and the E3 level concentration is two orders of magnitude lower than the concentration of interstitial iron. The origins of these levels are probably loosely associated iron-related complexes such as iron-acceptor pairs.