Influence of extended structural defects on the characteristics of electroluminescence in efficient silicon light-emitting diodes

We report our results on electroluminescence in the range of 1.0-1.6 mum, structural defects and electrophysical properties of light-emitting diodes fabricated by boron ion implantation into n-Si substrates at different concentrations of the doping impurity with a subsequent thermal annealing at 700-1200degreesC in argon or a chlorine-containing atmosphere. A band-to-band emission peak dominates in the luminescence spectra of all the samples at 80-500 K. The quantum efficiency of the band-to-band luminescence and the minority carrier lifetime increase with annealing temperature to 1100degreesC in argon, with the efficiency practically proportional to the lifetime. A similar correlation was observed after annealing in the chlorine-containing atmosphere. The maximum internal quantum efficiency (similar to 0.4%) was registered after annealing in argon at 1100degreesC, when there are no extended structural defects. Rod-like defects, partial Frank and perfect prismatic dislocation loops are formed after annealing at lower temperatures. Their type, sizes and density are governed by the annealing temperature. No correlation between the quantum efficiency and the defect structure was revealed with the variation of the annealing temperature. The analysis of the experimental data shows that the influence of extended defects on the band-to-band luminescence is most likely to be due to the incorporation and/or gettering of non-radiative recombination centers rather than to preventing the diffusion of charge carriers to the centers. The effect of the annealing conditions and doping impurity concentration in the substrates on the parameters of defect-related emission lines has also been studied. The most intensive defect-related electroluminescence at room temperature is observed after annealing at 700degreesC in diodes with a lower concentration.