Photoluminescence decay time and electroluminescence of p-Si/β-FeSi2 particles/n-Si and p-Si/β-FeSi2 film/n-Si double-heterostructures light-emitting diodes grown by molecular-beam epitaxy

We have epitaxially grown Si/beta-FeSi2/Si (SFS) structures with beta-FeSi2 particles on Si(001), and SFS structures with beta-FeSi2 continuous films on both Si(001) and Si(111) substrates by molecular-beam epitaxy. All the samples exhibited the same photoluminescence (PL) peak wavelength of approximately 1.54 mu m at low temperatures. However, the PL decay times for the 1.54 mu m emission were different, showing that the luminescence originated from different sources. The decay curves of the SFS structures with beta-FeSi2 continuous films were fitted assuming a two-component model, with a short decay time (tau similar to 10 ns) and a long decay time (tau similar to 100 ns), regardless of substrate surface orientation. The short decay time was comparable to that obtained in the SFS structure with beta-FeSi2 particles. The short decay time was due to carrier recombination in beta-FeSi2, whereas the long decay time was probably due to a defect-related D1 line in Si. We obtained 1.6 mu m electroluminescence (EL) at a low current density of 2 A/cm(2) up to around room temperature. The temperature dependence of the EL peak energy of the SFS diodes with beta-FeSi2 particles can be fitted well by the semiempirical Varshni's law. However, EL peak positions of the SFS diodes with the beta-FeSi2 films showed anomalous temperature dependence; they shifted to a higher energy with increasing temperature, and then decreased. These results indicate that the EL emission originated from several transitions. (c) 2007 American Institute of Physics.