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Wannier-Stark effect and electron-phonon interaction in macroporous silicon structures with SiO₂ nanocoatings

Karachevtseva L., Goltviansky Y., Kolesnyk O., Lytvynenko O., Stronska O.

Opto-Electronics Review

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2014

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Vol. 22, No. 4

201-206

EN

We investigated the contribution of electron-phonon interaction to the broadening parameter of the Γ Wannier-Stark lader levels in oxidized macroporous silicon structures with different concentration of Si-O-Si states (TO and LO phonons). The obtained value of the Wannier-Stark ladder Γ parameter is much less than the djacent level energy evaluated from giant oscillations of resonance electron scattering on the surface states. We determined the influence of broadening on the oscillation amplitude in IR absorption spectra as interaction of the surface multi-phonon polaritons with scattered electrons. This interaction transforms the resonance electron scattering in samples with low concentration of Si-O-Si states into ordinary scattering on ionized impurities for samples with high concentration of Si-O-Si states. The transformation takes place at the scattering lifetime coinciding with the period of electron oscillations in the surface electric field.

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Photocarrier transport in 2D macroporous silicon structures

Karachevtseva L., Onyshchenko V., Sachenko A.

Opto-Electronics Review

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2010

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Vol. 18, No. 4

394-399

EN

The mechanisms of photocarrier transport through a barrier in the surface space-charge region (SCR) of 2D macroporous silicon structures have been studied at photon energies comparable to that of the silicon indirect band-to-band transition. It was found that the photoconductivity relaxation time was determined by the light modulation of barrier on the macropore surface; as a result, the relaxation itself obeyed the logarithmic law. The temperature dependence of the photoconductivity relaxation time was determined by the thermionic emission mechanism of the current transport in the SCR at temperatures T > 180 K, and by the tunnel current flow at T < 100 K, with temperature-independent tunnelling probability. The photo-emf was found to become saturated or reverse its sign to negative at temperatures below 130 K because of light absorption due to optical transitions via surface electronic states close to the silicon conduction band. In this case, the surface band bending increases due to the growth of a negative charge of the semiconductor surface. The equilibrium electrons in the bulk and photoexcited holes on the macropore surface recombine through the channel of multistage tunnel recombination between the conduction and valence bands.

3

Photonic band structure of oxidized macroporous silicon

Glushko A., Karachevtseva L.

Opto-Electronics Review

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2006

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Vol. 14, No. 3

201-203

EN

We investigated theoretically the effect of surface silicon oxide layer on the photonic band structure of a macroporous silicon photonic crystal. Using the plain wave method we have shown that the bandgap in oxidized structure is shifted to the higher frequencies relative to non-oxidized case. We also demonstrate that comparatively wide absolute bandgap can be obtained for low air filling fractions by using thick SiO2 layer. As an example of possible application of such three-component systems, we have shown the concept of a selector of electromagnetic modes based on our calculations.