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Proceedings Paper

Optically active Si surfaces
Author(s): Zbigniew T. Kuznicki; Jean-Yves Bigot
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Paper Abstract

The optoelectronics and photonics properties of silicon are fundamentally influenced by the density of carriers present near the sample surface. One way of generating very large densities of such carriers is to confined them in a Si monolayer made by implantation in an amorphous Si (Si-a) nanolayer followed by a suitable thermal treatment. In that way, one can photo-generate a two dimensional (2D) plasma which modifies the complex refractive index of the nanolayer. Our work describes the modification of the reflection and absorption induced by incident light in the same devices when varying their electronic passivation. The different studied samples contain a buried amorphous substructure and are distinguishable exclusively by the thickness of the SiO2 covering layer. The measurements of the different samples show large differences in their absorption coefficients. The absorption coefficient α measured at 450 nm for a Si sample with a thin passivation layer is α~4.0x104 cm-1 that is nearly 5 times lower than a sample which is processed with a complementary passivation α~1.8x105 cm-1. In both cases average flux of photons (1015 s-1 cm-2) is the same. This result confirms the role of the free-carrier population, induced by the incident light, which is confined near the surface. In the conventional modeling of the absorption only the surface recombination rate governed by the thickness of the SiO2 covering layers has to be taken into account. In the present work, we show that the carrier confinement also plays an important role. Such results are very interesting in the context of optoelectronics and photonics silicon nano-structured devices.

Paper Details

Date Published: 5 May 2008
PDF: 8 pages
Proc. SPIE 7002, Photonics for Solar Energy Systems II, 70020R (5 May 2008); doi: 10.1117/12.781524
Show Author Affiliations
Zbigniew T. Kuznicki, Photonic Systems Lab., ENSPS Pôle API Parc d’Innovation (France)
Jean-Yves Bigot, Institut de Physique et Chimie des Matériaux de Strasbourg, Univ. Louis Pasteur (France)

Published in SPIE Proceedings Vol. 7002:
Photonics for Solar Energy Systems II
Andreas Gombert, Editor(s)

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