Optical Study of the Anisotropic Confinement of Excitons in GaAs/AlGaAs Quantum Dots

Masakazu Yamagiwa, Nobuyuki Koguchi, Fumiyoshi Saito, Yoshihiro Ogawa, Fujio Minami
2006 e-Journal of Surface Science and Nanotechnology  
Anisotropic confinement of excitons in a single GaAs/Al0.405Ga0.595As quantum dot (QD) is studied using micro-photoluminescence (micro-PL) measurements. In this study, a low-density GaAs QD sample is prepared by Modified Droplet Epitaxy (MDE). The QDs are anisotropic in shape and relatively large. This low density sample is combined with micro-PL spectroscopy to obtain single QD spectra. From the single GaAs QD micro-PL spectrum-excitation density dependence, an initial blue shift of
more » ... ly 100 µeV is seen for the main peak with increasing excitation density, and as the excitation density is further increased, an overall red shift of approximately 200 µeV is seen. A similar red shift is seen for the multi-excitonic lines. The blue shift can be attributed to a repulsive interaction related to the Pauli Exclusion Principle governing the behavior of the electrons and holes which comprise the excitons, and is a manifestation of the one dimensional nature of the linearly-aligned excitons in these QDs. The red shift can be attributed to an attractive Van der Waals interaction between confined excitons, which increases as the exciton density increases. The anisotropic confinement of excitons is probed by the magnetic field, excitation density, and photoluminescence (PL) polarization dependence of the single QD micro-PL spectrum. It is found that the anisotropic confinement, as well as the large QD size, are responsible for this lack of balance between repulsive forces due to the Pauli Exclusion Principle and van der Waals attractive forces.
doi:10.1380/ejssnt.2006.446 fatcat:aqulvdx4pzfobn33qfsa7la3e4