Dislocation luminescence in plastically deformed silicon crystals: effect of dislocation intersection and oxygen decoration

This paper is addressed to the discussion of the effect of the dislocation structure and the impurity contamination on the photoluminescence of Czochralski (Cz) silicon in the range of the D1 emission at 0.8 eV. Two types of dislocation systems were considered. One consists of intersecting hexagonal half loops of screw and 60degrees segments. The other one consists of a set of non-intersecting, parallel 60degrees dislocations. In both cases the plastic deformation processes were carried out at 670degreesC, taking care to avoid unwanted impurity contamination. It is shown that the PL emission of pure 60degrees dislocations in the D1 region is missing the 0.807 eV component and consists of a narrow band at 0.817 eV superimposed onto a broad background centered at 0.830 eV. It is also shown that a system of intersecting half loops presents both the 0.807 eV and the 0.817 eV components. The effect of thermal annealing at 800degreesC was shown to induce oxygen precipitation effects, revealed by supplementary spectral features. It is eventually demonstrated that the set up of the D1 band is not necessarily connected with the contamination of 60degrees dislocations with metallic impurities. The major role of oxygen on the dislocation luminescence is eventually experimentally confirmed.