Publication
The properties of semiconductors heterostructures of nanoscopic dimensions change from that of bulk material according to the rules of quantum mechanics. The planar quantum wells (QWs) are widely used in various diode and laser devices thanks to the relative ease of fabrication and to their improved electronic and optical performance compared to bulk materials. Quantum effects become more apparent when the charge carriers are confined in more than 1 spatial dimension. Much scientific interest was initially dedicated to the quantum wire (QWR) structures, which confine carriers into a quasi-1D space. But their sensitivity to disorder and the development of efficient fabrication methods of quantum dots (QD) shifted the attention to this latter system. The carrier confinement in the three directions of space confers to these structures a discrete spectrum of energy states, with the state occupancy ruled by the Pauli exclusion principle. The prospective applications are numerous in domains such as ultra-low threshold lasers, quantum cryptography, true random numbers generation, quantum electrodynamics experiments, etc. One of the prominent semiconductor growth techniques is the metalorganic vapour phase epitaxy (MOVPE). We used this method to produce ordered QWRs and QDs at the bottom of V-shaped and tetrahedral recesses, respectively. These nanostructures form by the complimentary actions of nano-capillarity and growth rate anisotropy in these recesses etched in GaAs substrates. This fabrication process offers some key advantages over other methods. The emission energy is very well controlled, with a narrow inhomogeneous broadening and a high uniformity across the wafer. Combined with the highly precise control on the formation site, this offers the possibility of high-yield integration of one or even several nanostructures, e.g., into photonic crystal devices. Other advantages of this approach are the impressive tunability of the electronic potential within the nanostructures and the possible use of well-defined intraband transitions. However, the emission energy of V-groove QWRs and pyramidal QDs studied so far is quite limited due to the formation mechanism imposing a low degree of strain. Incorporation of nitrogen has dramatic effects on the band structure of GaAs-based materials. Dilute concentrations (< 5 %) lead to a huge shrinkage of the bandgap, as well as to large changes in various other electronic properties. Addition of nitrogen into QWRs and QDs nanostructures may thus allow emission wavelengths above 1 μm, possibly up to the 1.3 μm telecommunication window of silica optical fiber. In view of these opportunities, the first part of this work is dedicated to the study of N incorporation into QWs grown on vicinal-(100) GaAs substrates. The substrate miscut angle is often neglected in growth studies, and is of great importance in the cases of V-grooves and pyramidal recesses because of the large misorientations of the recesses facets. In ou