Temperature dependence of luminescence efficiency, exciton transfer, and exciton localization in GaAs/AlxGa1−xAs quantum wires and quantum dots

By studying the temperature dependence of the photoluminescence intensity in strain-confined GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As quantum wires and quantum dots, we show that as dimensionality is reduced from two-dimensional (2D) through 1D to 0D, there is no reduction of luminescent efficiency at low temperature, and that high quantum efficiency persists to significantly higher temperature. There is efficient spatial energy transfer from the 2D region to the 1D or 0D region. This transfer increases with temperature, showing that there is a barrier to transfer a few meV high. This barrier is lower than theoretically predicted. For above band-gap excitation there is substantial ``capture transfer'' in which unthermalized carriers or excitons transfer even at very low temperature. Exciton localization due to the well-width fluctuations of the host quantum well also plays an important role in determining the temperature dependence of the exciton transfer in these structures.