Exciton capture and losses in a stacked submicron array of sidewall quantum wires on patternedGaAs(311)Asubstrates

The optical properties of stacked GaAs/(Al,Ga)As quantum wire arrays, with a 0.5 μm lateral period fabricated by molecular beam epitaxy on patterned $\mathrm{GaAs}\mathrm{}\left(311\right)A$ substrates, have been investigated. We observe an unexpectedly high quantum wire related contrast in the lateral distribution of the cathodoluminescence (CL) intensity, in particular at 300 K. The temperature dependence of this contrast as well as of the integrated CL intensities in the quantum wires and connecting quantum wells, reveals the loss mechanisms, which cause a reduction of the exciton transfer efficiency from the well into the wire regions. For low and intermediate temperatures, exciton localization and nonradiative recombination within the quantum well regions contribute to the decrease of the transfer efficiency. Near room temperature, the vertical escape of carriers, in particular out of the quantum well regions into the (Al,Ga)As barriers, is the limiting process. Within the framework of a detailed model, we determined the transfer time and the ratio of the radiative recombination times in the well and wire regions by combining the spatially resolved CL measurements with time-resolved photoluminescence spectroscopy.