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 µm at low temperatures. However, the PL decay times for the 1.54 µm 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~10 ns) and a long decay time (tau~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 µm electroluminescence (EL) at a low current density of 2 A/cm2 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\u27s 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