Exciton and carrier dynamics in indirect-band-gap semiconductor nanostructures with a type-I band alignment

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A novel class of semiconductor nanostructures, in particular quantum dots and quantum wells, with a type-I band alignment and an indirect band gap in the momentum space will be investigated. The nanostructures will be fabricated from various III-V materials, and different kinds of optical as well as magneto-optical techniques shall be used to examine their electronic band structure and the mechanisms of electron and exciton energy and spin relaxation and recombination. Special attention will be drawn to the scenarios where the direct Gamma valley of the conduction band electrons is tuned by the spatial confinement to the energy of the indirect X or L valley. The resultant Gamma-X and Gamma-L mixed electron states are expected to strongly modify the recombination and spin dynamics of the indirect excitons and carriers. Theoretical models of the mixed electron states, their wave functions and matrix elements for optical transitions will be developed; in that context, model calculations of the electronic structures will be performed.