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Nicolas Pauc

Exciton condensation in silicon nanostructure

Published on 8 October 2004
Thesis presented October 08, 2004

This work deals with the study of the different electron-hole phases created in silicon nanostructures at low temperature under ultra-violet illumination. Thanks to wavelength and time resolved photoluminescence techniques the exciton, electron-hole liquid and electron-hole plasma phases are clearly identified in such structures. The first two chapters give the necessary information to understand the physics of the condensation of excitons in bulk semiconductors. The experimental part developped in the following chapters concerns the spatial confinement of the liquid in Si/SiO2 2 heterostructures obtained with Silicon On Insulator SOI (chapter three). The nucleation and coalescence of liquid droplets and a change in the condensation threshold are observed in these samples. The photoluminescence lineshape analysis gives the liquid equilibrium parameters (density, temperature). The chapter four shows that the three dimensional confinement obtained in sub-micronic boxes made on SOI involves an increase in the liquid-plasma transition temperature (pressure cooker effect). The chapter five deals with the influence of the electric field on the electron-hole liquid in SOI quantum wells. A redshift of the recombination line is observed due to the band curvature of the semiconductor in the Schottky junction. Finally, the chapter six deals with the study of the effect of quantum confinement on the liquid in thin wells. Data are analyzed with a model that takes account of the lowering of the dimensionality and the dielectric mismatch between the well and the barrier. The transition between ultra-thin SOI quantum wells and nanocrystals has been observed.

electron-hole liquid, electron-hole plasma, silicon, spatial confinement, quantum confinement, exciton, silicone, nanostructure, SOI, photoluminescence

On-line thesis.