Interaction of α-radiation induced defects with Pd-related deep levels in silicon

Abstract

Results of a detailed deep level transient spectroscopy study of Pd-doped p+n Si diodes irradiated with 5.48 MeV α particles are presented, which also include investigations of isochronal annealing behavior of the deep level spectra up to a temperature of 350–400 °C. An extended comparison with results obtained on reference samples as well as with previously published results of deep level studies on Pd-doped samples (unirradiated) and on undoped α-irradiated samples provides valuable information, since the same starting material is used in all these studies. It is observed that, in general, the Pd-related deep levels increase in concentration upon irradiation at the expense of α-radiation-induced levels. In particular, the A center sharply decreases in concentration upon post-irradiation annealing with a corresponding increase in the concentration of the dominant Pd-related level. The results also show that, contrary to the previously held belief, two well-known Pd-related levels at Ec−0.37 eV and Ec−0.59 eV are not states of the same defect and an off-center/on-center substitutional Pd-vacancy model for the defects corresponding to Ec−0.18 eV and Ec−0.22 eV Pd-related levels cannot explain new data presented here. In the reference (undoped, heat treated) samples, a few levels are observed after α-irradiation or post-irradiation annealing which were not detected in the untreated diodes, pointing to their relationship to quenched-in defects. A new annealed-in hole level H(α-Pd) at Ev+0.27 eV is observed which seems to be a complex of Pd with some α-irradiation-induced defect.