Growth control, structural characterization, and electronic structure of Stranski-Krastanow indium arsenide/gallium arsenide(001) quantum dots

This dissertation contributes to the subject of formation and properties of semiconductor quantum dots (QDs) based on coherent three-dimensional (3D) islands formed during lattice-mismatched heteroepitaxy of InAs on GaAs(001). Research carried out clarifies the following aspects: InAs island formation kinetics and its control to improve size uniformity of QDs; structural examination of island geometry with transmission electron microscopy (TEM) and atomic force microscopy (AFM) to extract QD density, size, and shape; accessing QD electronic structure via power- and temperature-dependent photoluminescence (PL) and PL excitation (PLE) techniques, with extraction of electronic structure-related and carrier relaxation dynamics-related parameters for comparison with theoretical predictions and for guidance in design of QD-based applications.; Innovative stress-engineering approaches, such as punctuated island growth (PIG) or variable deposition amount (VDA), are introduced here and have allowed independent control on island density and island size, generating samples with remarkable QD size uniformity and larger average size. Structural and optical evidence for a change in the InAs island shape to steeper sidewalls at a self-limiting lateral size, and the pathway of such transformation, is demonstrated.; PL and size-selective PLE are employed to investigate ground state transitions, excited state transitions, and quantum-size effects in such QDs. Anti-Stokes photoluminescence and temperature-dependent measurements show that the PLE spectra reflect the absorption spectra of QDs rather than the relaxation pathways. Temperature-dependent PL peak position, intensity, and linewidth provide information on QD ground state localization and on dynamics of carrier redistribution within QD ensemble. High power density photoluminescence reveals renormalization of the QD transition energies due to correlation/exchange interaction of the localized excitons, in addition to the well-known state-filling effects. Phonon-assisted exciton transitions demonstrate an unexpectedly enhanced exciton-LO-phonon interaction in these large InAs/GaAs QDs, attributed to particular low symmetry and the piezoelectric effect. Finally, spacer thickness and composition dependent excitation transfer processes within quantum dot pairs in bilayer InAs/GaAs QD samples are investigated in detail.