Abstract : Combining direct bandgap III-V compound semiconductors, such as InAs and GaAs, with silicon to realize on-chip optical light emitters and det ectors at telecommunication wavelengths is an important technological objective. However, traditional thin film epitaxy of InAs and GaAs on silicon is challenging because of the high lattice mismatch between these materials. Nanowires can overcome this limitation. Indeed, their free lateral surface efficiently releases the mismatch strain via elastic lateral relaxation. In this thesis, I first demonstrate the growth of axial GaAs/InAs nanowire heterostructures on a silicon substrate. I grew nanowires by gold-assisted vapor liquid solid mechanism, in a molecular beam epitaxy reactor. The nanowires were then characterized using energy dispersive x-ray spectroscopy and transmission electron microscopy to evaluate their composition and crystalline structure. The strain distribution around the GaAs/InAs interface was studied experimentally using geometrical phase analysis and compared to numerical simulations, performed with the COMSOL software. To realize these structures, I tackled different challenges inherent to axial nanowire heterostructures, such as kinking during material exchange, compositionally graded interfaces, and radial overgrowth.

Contact : moira.hocevar@neel.cnrs.fr