Dynamical processes on high density indirect and direct excitons in AlxGa1−xAs/AlAs quantum wires

Under intense light excitation, dynamical processes on indirect and direct excitons (DEs) at high density in AlxGa1−xAs/AlAs quantum wire (QWR) structures have been investigated. The high density effects are characterized by the spectral blue-shifts for both the types of excitons, appearing at quite different excitation densities in the two types. In a type-II QWR structure, a large blue-shift of the indirect exciton (IE) photoluminescence appears under a heavy excitation density, but that of the higher lying direct one does hardly. Though those excitons of the two types coexist simultaneously in the QWR structure, only the IE shows the high density effects and the DE does not. For the origins of the blue-shifts, the phase space filling effects on the conduction and valence bands as well as the electric field effect due to the separation mechanism of the carriers in the type-II structure are taken into account. The excitation dynamics of the high density IEs in the QWR via the QW in the terrace structure to the Γ- and X-point in the QWR is discussed.