Deterministic growth and characterization of quantum dots for quantum computation

This report describes the growth of semiconductor self-assembled quantum dots. The dimensions of these nanostructures are small enough that their properties approach those of atoms: the spatial confinement of carriers leads to quantized energy levels. In(Ga)As quantum dots grown on a GaAs substrate are studied here. They are fabricated using molecular beam epitaxy via Stranski-Krastanov growth. The objective of the internship is to optimize MBE growth to obtain a low and uniform density. The growth season having started during the internship, it was first necessary to calibrate the MBE system. Thin film growth rate calibration using RHEED device aims to determining the fiability of the temperature and flux measurements by a thermocouple and a pressure gauge respectively. The optimization of growth conditions (namely substrate temperature and growth rate) is based on the study of quantum dots density and morphology by atomic force microscopy. The non-uniform distribution on the sample is due to inhomogeneity on substrate temperature and flux. Quantum dots optical properties have been studied by photoluminescence. An optical system has been set up to observe the quantum dots light emission, and thus get the exact position of quantum dots over the sample.