Characterization of deep levels introduced by alpha radiation in n-type silicon

Abstract

A detailed deep-level transient spectroscopy study of the characteristics of deep-level defects introduced by 5.48 MeV alpha particles in low-doped n-Si is reported. The deep-level characteristics studied include emission rate signatures, activation energies, capture cross sections and their temperature dependence, and defect concentrations and their spatial profiles. At least five deep levels in the upper-half band gap and two levels in the lower-half gap have been observed as a result of irradiation and characterized in detail. A systematic study of their generation rates up to a dose of about 3×1010 alpha particles/cm2 has been performed providing insights into the dose dependence of their formation mechanisms. Interesting room temperature transformation phenomena have been observed in our deep-level spectra during room temperature storage of the irradiated samples. Extensive isochronal thermal annealing measurements have been carried out to obtain data on the anneal-out characteristics of the radiation-induced deep levels and to identify these with the known defects wherever possible. A number of new annealed-in levels have been observed during this investigation. A detailed comparison with the published results is presented.