Optically active Si surfaces

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 confine them in a Si nanolayer made by implantation followed by a suitable thermal treatment. In that way, one can photo-generate a two dimensional (20) plasma which modifies the complex refractive index of the nanolayer.Our work describes the modification of the reflec tion and absorption induced by incident light in the same devices when varying their electronic passivation. The different studied samples contain a buried amor phous substructure and are distinguishable exclusively by the thickness of the Si02 covering layer.The measurements of the different samples show large differences in their absorption coefficients. The absorption coefficient a measured at 450 nm for a Si sample with a thin passivation layer is a -4.0x10 4 cm-1 that is nearly 5 times lower than a sample which is processed with a complementary passivation a -1.8x1 05 cm-1 . In both cases average flux of photons (10 15 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 conven tional modeling of the absorption only the surface re combination rate governed by the thickness of the Si02 covering layers has to be taken into account [1). In the present work, we show that the carrier confinement also plays an important role. Such results are very interest ing in the context of optoelectronics and photonics sili con nanostructured devices.

Size distributions of chemically synthesized Ag nanocrystals

“…The solar spectrum convertible by crystalline silicon cells lies between 370 and 1100 nm (100 nm corresponds to ∼1.1 eV, which is the band gap of Si) 23 . It is desirable to have a broad scattering peak at a wavelength where the Si absorbs most of the light.…”

Dielectric functions and optical parameters of heavily doped and/or highly excited Si:P

“…Specific optoelectronic properties of heavily doped and/or highly excited semiconductors, which differ in various ways from perfectly known (non-degenerated) materials, lead to new often unpredicted applications [14,15]. The properties of such materials find use and are appreciated in late generation electronic circuits, and will probably appear in future all-Si optical and photonic applications.…”