The photoluminescence (PL) technique has been applied for the first time to the characterization of shallow impurities in Si epitaxial crystals and of nitrogen in bulk Si crystals. The species of impurities incorporated intentionally or unintentionally in an epitaxial layer can be definitely determined by the PL analysis. The new PL line at 1.1223±0.0001 eV observed in N-doped crystals is identified to be due to nitrogen. Epitaxial samples show a quantitative relationship between the intensity ratio of the PL line from an epitaxial layer to that from its substrate and the impurity concentration in the epitaxial layer. In N-doped crystals, the PL intensity ratio between the intrinsic and the 1.1223 eV lines increases linearly with the N concentration. It is demonstrated that these PL intensity ratios can be used as measures of the respective impurity concentrations.
Read full abstract