Two-exciton state in GaSb∕GaAs type II quantum dots studied using near-field photoluminescence spectroscopy

The authors report on the photoluminescence spectroscopy of a single GaSb∕GaAs type II quantum dot (QD) at 8K. A sharp exciton emission with a linewidth of less than 250μeV was observed. Two-exciton emission at the higher energy side of the exciton emission indicates that the two excitons in a type II QD do not form a bound biexciton. The energies of the exciton and two-exciton states were calculated using an atomic pseudopotential model, which provides a quantitative description of the antibound nature of the two-exciton state in type II QDs.