Highly [110]∕[101]-oriented semiconducting iron disilicide β-FeSi2 continuous films were grown on Si(111) by molecular-beam epitaxy (MBE) using a β-FeSi2 epitaxial template formed by reactive deposition epitaxy. The optimum MBE growth temperature was determined to be about 750°C. At this temperature, the full width at half maximum β-FeSi2(220)∕(202) x-ray diffraction peak was at a minimum. Subsequent MBE overgrowth of an undoped Si layer was performed on the β-FeSi2 at 500°C, resulting in the Si∕β-FeSi2∕Si double heterostructure. After annealing the wafers at 800°C in Ar for 14h, 1.55μm photoluminescence (PL) was obtained at low temperatures. Time-resolved PL measurements elucidated that the luminescence originated from two sources, one with a short decay time (τ∼10ns) and the other with a long decay time (τ∼100ns). The short decay time was thought to be due to carrier recombination in β-FeSi2, whereas the long decay time was due probably to a dislocation-related D1 line in Si.

We have fabricated p-Si/β-FeSi2 film/n-Si double-heterstructure (DH) light-emitting diodes (LEDs) on Si(111) substrates by molecular beam epitaxy (MBE). It was found that both the thickness of an undoped Si overlayer and subsequent annealing temperature were key parameters in preventing the aggregation of the β-FeSi2 film and the successful formation of a Si/β-FeSi2 film/Si DH LED on Si(111). A 1.6 µm electroluminescence (EL) was realized at room temperature (RT) at a current density higher than 78 A/cm2 by increasing the thickness of the β-FeSi2 active region from 90 nm to 250 nm, suggesting that there exist numerous defects at Si/β-FeSi2 heterointerfaces.

Si/β-FeSi2 particles/Si(001) and Si/β-FeSi2 film/Si(111) structures were grown by reactive deposition epitaxy (RDE) and by molecular beam epitaxy (MBE), and time-resolved photoluminescence (PL) was measured from 8 K to 150 K. Both samples exhibited the same PL peak wavelength of 1.54 µm at low temperatures, but the PL decay time of 1.54 µm emission was different, showing that the luminescence originated from different sources. A short decay time (τ∼10 ns) was found to be dominant for the Si/β-FeSi2 particles/Si(001) at low temperatures. In contrast, the decay curve of the Si/β-FeSi2 film/Si(111) was well fitted by assuming a two-component model, with a short decay time (τ∼10 ns) and a long decay time (τ∼100 ns).

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We report on the long-term reliable CW operation of high-power and high-efficiency 915-nm broad-area laser diodes (BA-LDs). An output power of over 20 W and a maximum power-conversion efficiency of over 65% have been marked at a heat-sink temperature of 20 ºC. Stable operations of over 5000 h have also been achieved for the 915-nm and 976-nm BA-LDs with CW output powers of 20 W, respectively. The window structure with a band gap difference of 100 meV provides the reliable operation at the high-output power range.