Optical Studies of InAs Quantum Dots in III-V Semiconductors
Abstract: I this thesis, optical studies of InAs quantum dots (QDs) in GaAs and InP are presented. The electronic structure of these zero dimensional structures, grown in the Stranski-Krastanow growth mode, was studied by photoluminescence spectroscopy (PL), junction space-charge techniques (JSCT) and photoconductivity (PC) measurements. For the InAs/GaAs system we present single-dot photoluminescence spectra for different excitation power densities and temperatures. These spectra show level splitting due to few-particle effects. We also present calculations including both direct and exchange interaction for systems up to three excitons in the dot. We were able to assign different emission lines to transitions between different multiple exciton states. A rate equation model was developed which allows simulations of the peak intensities with excitation power density to be made and compared with experimental results. The InAs/InP system was investigated using PL spectroscopy, JSCT, and PC measurements. In contrast to other systems the holes were found to be more strongly confined than the electrons. We have also performed photoluminescence measurements revealing excited states in good agreement with theory. For both systems we studied the possibility to manipulate the positioning and size of the QDs. The growth results were investigated using atomic force microscopy (AFM) and PL measurements
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