Study of the insertion of dopants in group IV based semiconductor nano-objetcs : from hyperdoping to lamellar alloys

Abstract :

This thesis concerns the study of the structural and optical properties in P-doped SiO/SiO2 multilayers and thin layers of SiP and GeP. They are prepared by evaporation under ultrahigh vacuum. After annealing, Si nanocrystals formation is observed in P-doped SiO/SiO2 multilayers. P atoms are mainly located in Si nanocrystals’ core with concentrations reaching up to 10 at.%, i.e. well beyond the solid solubility limit of P in bulk Si. Infrared absorption measurements give evidence of a localized surface plasmon resonance. The variation of phosphorus concentration allows to tune its position. Simulations, based on the Mie theory, permit to determine both the free charge carrier density, from which a dopant activation rate of about 5% is obtained, as well as the mobility of about 23,5 cm2V-1s-1.

To prevent the phosphorus desorption and diffusion in the Si substrate, the Si :P thin film is grown between two 20nm thick SiO2 layers. The SiP compound formation is observed after an annealing process higher than 950°C . SiP crystallizes in an orthorhombic structure in the Cmc21 space group. The thin films are composed of SiP grains with a size close to the micrometer scale which coexist with Si grains containing 1 to 2% of phosphorus. The lamellar structure of SiP was identified. The first liquid phase exfoliation test was performed after an etching to remove SiO2 surface layer and the doped silicon. It is shown that it is possible to detach SiP flakes from the Si substrate. The GeP compound, which is obtained after a 500°C annealing, crystallizes in a monoclinic structure in the C2/m space group. The thin films are mainly composed of GeP grains which coexist with small Ge grains close to the surface. As SiP, GeP is lamellar and the liquid phase exfoliation leads to GeP flakes tear off from the Si substrate.

Keywords : Thin films, evaporation, phosphorus hyperdoping, silicon nanocrystals, plasmon, Sip, GeP.

 

M. Jérôme Plain - Rapporteur - Professeur à l’Université de Technologie de Troyes - L2N, Troyes
M. Bruno Masenelli - Rapporteur - Professeur à l’INSA - INL, Lyon
Mme. Caroline Bonafos - Examinatrice - Directrice de recherche au CNRS - CEMES, Toulouse
M. Aotmane En Naciri - Examinateur - Professeur à l’Université de Lorraine - LCP-A2MC, Metz
M. Hervé Rinnert - Directeur de thèse - Professeur à l’Université de Lorraine - IJL, Nancy
M. Mathieu Stoffel - Codirecteur de thèse - Maître de Conférences à l’Université de Lorraine - IJL, Nancy