Temperature dependence of electroluminescence from Si-based light emitting diodes with β-FeSi2 particles active region

Electroluminescence (EL) properties of Si-based light emitting diodes with β-FeSi₂ particles active region grown by reactive deposition epitaxy are investigated. EL intensity of β-FeSi₂ particles versus excitation current densities has different behaviors at 8, 77 K and room temperature, respectively. The EL peak energy shifted from 0.81 to 0.83 eV at 77 K with the increase of current density from 1 to 70 A/cm². Temperature dependence of the peak energy can be well fitted by semi-empirical Varshni's law with the parameters of α=4.34 e-4 eV/K and β=110 K. These results indicate that the EL emission originates from the band-to-band transition with the band gap energy of 0.824 eV at 0 K.     

Conduction type and defect levels of β-FeSi2 films grown by MBE with different Si/Fe ratios

[1 0 0]-oriented β-FeSi₂ films were grown on Si(0 0 1) substrates by molecular beam epitaxy (MBE) with a deposited Si to Fe atomic ratio (Si/Fe ratio) varied from 1.6 to 2.8. It was found that the conduction type of the β-FeSi₂ films changed from p- to n-type between the deposited Si/Fe=2.4 and 2.8. Rutherford Back Scattering (RBS) measurements revealed that the real Si/Fe ratio of β-FeSi₂ is 2.0–2.1 for all the samples after 900°C annealing for 14 h, showing that stoichiometry of the grown films is almost satisfied even though the deposited Si/Fe ratio was away from stoichiometry.