Atomistic Pseudopotential Calculations of Thickness-Fluctuation GaAs Quantum Dots

We calculate the electronic and optical properties of thickness-fluctuation quantum dots of different sizes and elongations using an atomistic empirical pseudopotential approach and configuration interaction. The carriers are confined by a monolayer fluctuation in the thickness of a GaAs/Al0.3Ga0.7As quantum well with a nominal thickness between 10 and 20 monolayers. For 10 monolayer thickness, we find several confined electron and hole levels of dominant heavy-hole character penetrating deep into the barrier (out of plane) and far beyond the physical dimension of the monolayer step (in-plane). The spatial extent of the states is strongly affected by the random-alloy fluctuations of the barrier, pushing the states toward Ga-rich regions of the interface. The similarity in the spatial extent of the electron and hole states leads to strong oscillator strength and a rich optical spectrum. The exciton as well as biexciton and trions (positive and negative) all show several lines in absorption despite the very shallow confinement potential given in these structures. The effects of correlations is drastic on the optical spectrum with the creation of highly correlated states that deviate strongly from the uncorrelated results.