Crossed excitons in a semiconductor nanostructure of mixed dimensionality

Abstract

Semiconductor systems of reduced dimensionality, e.g., quantum dots or quantum wells, display a characteristic spectrum of confined excitons. Combining several of these systems may lead to the formation of “crossed” excitons, and thus new equilibrium states and scattering channels. We derive gain excitation spectra from two-color pump-probe experiments on an In(Ga)As based quantum dot semiconductor optical amplifier by analyzing the amplitudes of the traces. This grants access to the quantum dot response, even in the presence of strong absorption by the surroundings at the excitation energy. The gain excitation spectra yield evidence of crossed quantum dot-bulk states.