Radioactive isotopes for photoluminescence spectroscopy -111In in silicon

A sample of high-purity silicon was implanted with the radioactive isotope 111In (τ1/2 = 2.8 d) to a total dose of 1011 atoms. The sample was rapidly thermally annealed and quenched to room temperature. The intense photoluminescence (PL) characteristic of Si:In (labelled PQR) produced by this treatment was found to decay non-exponentially and much faster than expected for the 111In half-life. The intensity of the neutral In acceptor bound exciton PL, on the other hand, decays roughly as expected. New features appear in the spectrum over periods of days and weeks. Although none of these can be directly attributed to daughter centres of the In PQR or substitutional acceptor centres, they are believed to be due to Cd impurities produced in the radioactive decay. A complex line structure and temperature dependence is observed for the new spectra. These results confirm the feasibility of using radioactive isotopes in PL spectroscopy, and they illustrate the power of the technique for defect analysis. (author)