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1

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.

2

Macroporous texturing of multicrystalline silicon for cells

Lipiński M.

Archives of Metallurgy and Materials

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2008

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Vol. 53, iss. 1

185-187

EN

It was shown that palladium deposited by immersion of Si wafers in PdCI, solution can be used as a catalyst for macro-porous formation by chemical etching of silicon. The light reflectance of silicon surface with macro-porous layer was considerably reduced in the whole region of 400-1000 nm. The lowest effective reflectivity of me-Si wafers with a new kind of texturization was equal to 4.2%. Presented method of texturization is very simple and can be used to improve the efficiency of multi-crystalline silicon solar cells.

PL

Zostało pokazane, że pallad osadzany na powierzchni krzemu z roztworu PdCl2 może być użyty w roli katalizatora w procesie wytwarzania krzemu makro-porowatego metodą trawienia chemicznego. Uzyskano znaczne obniżenie odbicia światła od powierzchni krzemu w całym zakresie długości fal 400-1000 nm. Najmniejsza wartość efektywnego współczynnika odbicia z nowym typem tekstury powierzchni wynosiła 4.2%. Przedstawiona metoda teksturyzacji jest bardzo prosta i może być wykorzystana do poprawy sprawności produkowanych fotoogniw z krzemu multi-krystalicznego.

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.