InP - based quantum dots for telecom wavelengths ranges

Long-distance quantum communication applications require sources of single photons, emitting at telecom wavelengths (around 1550 nm) with minimum attenu-ation losses of silica fiber. Semiconductor self-assembled InAs/InP-based quantum dots (QDs) are possible candidates to reach this spectral region. One of the challenges on the way is a QD asymmetry, which limits the fidelity of entangled photons. Therefore, morphological and optical properties of QDs should be improved in order to achieve the necessary quality and intensity level of emitted photons. In this dissertation QDs are grown in the ultra-high vacuum by using the solid-source molecular beam epitaxy. QDs are systematically characterized with low-temperature microphotoluminescence and other techniques. Different growth parameters and sample structures are optimized in order to achieve high-quality and low QDs density combined with the emission at telecom wavelength. Distributed Bragg reflectors and photonic crystal micro-cavities are also grown and fabricated in order to enhance QD emission. All necessary technical details and fundamental growth processes are included and discussed. Achieved state of the art results are a promising indication of InAs/InP QDs being used as an on-demand source of polarization-entangled photons. This PhD thesis is organized as follows: Chapter 1 contains brief introduction and motivation of the current work. Chapter 2 provides the necessary theoretical background. Chapter 3 is a description of experimental methods. In Chapter 4 experimental approach and results of the epitaxial growth process are described. Chapter 5 contains results of QDs integration with a distributed Bragg reflector, including statistical micro-photoluminescence measurements of self-assembled QDs. Growth, fabrication and characterization of photonic crystal microcavity structures with embedded single QDs are presented in Chapter 6. Finally, Chapter 7 summarizes the work.