Optical Spectroscopy of Novel Quantum Dot Structures

This thesis comprises works on novel quantum dot structures. New ways of growing III-V semiconductor quantum dots by integrating a ternary element or by growing on top of a silicon wafer are optically characterized, opening the way to more specific work on those new structures, while furthering our understanding of the epitaxy mechanisms behind them.

We study InGaAs/GaAs quantum dot structures monolithically grown on a silicon substrate, without use of germanium virtual substrate nor wafer bonding technique. Optical characterization of the sample with micro photoluminescence is performed and shows very good single quantum dot emission lines. Single photon emission from the InGaAs dots is demonstrated with photon correlation experiment showing clear anti-bunching. Photonic crystal cavities are fabricated for the first time with InGaAs dots monolithically grown on silicon and exhibit very high quality factor up to 13000 with a large percentage of cavities having Q-factors over 9000. This allows observation of Purcell effect for single photon emitting QDs and strong light-matter coupling between InGaAs QDs and cavities.

We also investigate unexpected emission lines on the same sample. The lines are identified as interface fluctuations in a GaAs/AlGaAs short period superlattice, making them the first Interface fluctuation quantum dots grown directly on silicon. Further optical characterization confirms the quantum dot nature of the emissions. Polarization measurements allow study of the fine structure splitting of exciton/bi-exciton pairs and the single photon emission of the dots is demonstrated.

Finally in a subsequent chapter we investigate InP/GaInP quantum dots with arsenic deposited during the growth process. Magneto-optic PL of samples with different concentrations of As allows to determine how the As changes the characteristics of the dots. Schottky diodes are fabricated and tested to show good characteristics, and electric field experiments demonstrate charge control over this new kind of dots.