D.L. Goroshko

Room temperature 1.5 μm light-emitting silicon diode with embedded β-FeSi2 nanocrystallites

Light-emitting silicon diode structures with embedded β-FeSi2 nanocrystallites have been fabricated using solid phase epitaxy and a combination of reactive deposition and solid phase epitaxy. Electroluminescence (EL) of the structures was studied over various temperatures and current densities under forward and reverse biases. The structures with nanocrystallites formed by the combined method exhibited EL at temperatures below 70 K only, suggesting the presence of a high concentration of defects—non-radiative centers. High-quality defect-free structures with nanocrystallites formed by solid phase epitaxy revealed intensive room temperature EL in energy range 0.76–1.08 eV at current densities as low as 1 A/cm2.

Characterization of the silicon/β-FeSi2 nanocrystallites heterostructures for the NIR photodetection at low temperature

Using solid phase epitaxy of thin Fe films and molecular beam epitaxy of Si, p-Si/β-FeSi2 nanocrystallites/n-Si(001) diode structure was fabricated. The diode exhibited a current responsivity of 15 mA/W and external quantum efficiency of about 1% at a wavelength of 1300 nm at 120 K without bias and 200 mA/W and 10%, respectively, at −30 V. The device specific detectivity calculated at 120 K in zero bias conditions of 2.1 × 1011 cmHz1/2/W at a wavelength of 1.3 µm is the highest ever reported for Si/β-FeSi2 systems. The Franz–Keldysh effect gives grounds for applying such systems not only for the development of optrons but also for that of electro-optical modulators.

VIS-NIR-SWIR multicolor avalanche photodetector originating from quantum-confined Stark effect in Si/β-FeSi2/Si structure

A Si n-i-p avalanche photodetector with embedded β-FeSi2 nanocrystals was developed. The device showed an ultrabroadband photoresponse from the visible (400 nm) to short-wavelength infrared (1800 nm) ranges. Specific detectivity at zero bias conditions reaches 2 × 109 cmHz1/2/W at 1300 nm and 2 × 108 cmHz1/2/W above 1400 nm at room temperature. Observed quantum-confined Stark effect together with avalanche multiplication resulted in a simultaneous two orders of magnitude increase in the photoresponse and spectral sensitivity expanding to 1800 nm when the device is operated in avalanche mode. The application fields of the proposed photodetector potentially include integrated Si photonics and multicolor photodetection; the quantum-confined Stark effect gives grounds for the development of fast-operated electro-optical modulators.

A room-temperature-operated Si LED with β-FeSi2 nanocrystals in the active layer: μW emission power at 1.5 μm

This article describes the development of an Si-based light-emitting diode with β-FeSi2 nanocrystals embedded in the active layer. Favorable epitaxial conditions allow us to obtain a direct band gap type-I band alignment Si/β-FeSi2 nanocrystals/Si heterostructure with optical transition at a wavelength range of 1500–1550 nm at room temperature. Transmission electron microscopy data reveal strained, defect-free β-FeSi2 nanocrystals of diameter 6 and 25 nm embedded in the Si matrix. Intense electroluminescence was observed at a pumping current density as low as 0.7 A/cm2. The device reached an optical emission power of up to 25 μW at 9 A/cm2 with an external quantum efficiency of 0.009%. Watt–Ampere characteristic linearity suggests that the optical power margin of the light-emitting diode has not been exhausted. Band structure calculations explain the luminescence as being mainly due to radiative recombination in the large β-FeSi2 nanocrystals resulting from the realization of an indirect-to-direct band ga...