• Halbwax, Mathieu

Abstract

Optical interconnects is a possible solution to solve the bottleneck of metallic interconnects in microelectronic chips. The aim of this thesis is to realize integrated Ge photodetectors in submicron SOI waveguides and more precisely the determination of an experimental protocol for the selective growth of thin relaxed Ge films on Si (001) by UHV-CVD technique. For optical interconnect applications, the Ge layers must exhibit a good crystalline quality within their whole thickness, an optical absorption coefficient at 1300 nm close to the Ge bulk one, and a weak surface roughness. To fulfill these criteria, the plastic relaxation process must be favored in order to occur within a Ge thickness as low as possible. As shown through the measurement in real time by electron diffraction of the film lattice parameter, this can be achieved at low growth temperature (330°C) after deposition of 16 nm. The low temperature film stabilizes for 30 nm and enables the re-growth of Ge at higher temperature (600°C) without roughening. The increase in growth temperature results in a much higher growth rate, in a drastic improvement in crystalline quality and in a fully relaxed material. The cooling down to room temperature induces a thermal tensile strain. The resulting gap reduction yields to increase the absorption threshold wavelength.The selective growth has also been obtained in SiO2/Si windows and on etched Si lines on SOI substrate using the Ge growth protocol. This thesis work has demonstrated the possibility to use Ge to realize integrated photodetectors on submicron SOI waveguides.

Topics

• impedance spectroscopy
• surface
• polymer
• electron diffraction
• Silicon
• chemical vapor deposition