Storage and retrieval of excitons were demonstrated with semiconductor self-assembled quantum dots (QDs). The optically generated excitons were dissociated and stored as separated electron-hole pairs in coupled QD pairs. A bias voltage restored the excitons, which recombined radiatively to provide a readout optical signal. The localization of the spatially separated electron-hole pair in QDs was responsible for the ultralong storage times, which were on the order of several seconds. The present limits of this optical storage medium are discussed.

We report photoluminescence (PL) spectra related to a two-dimensional electron gas confined at a GaN/AlGaN heterointerface. The recombination between electrons confined in the bottom of the interface potential and photoexcited holes causes a broad PL emission about 50 meV below the GaN exciton emissions. A second emission, attributed to the recombination of electrons in the first excited level at the interface, is also observed close to the excitonic band gap in GaN. The data agree with a self-consistent calculation of the energy levels and electron concentration at the interface.

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We present an InAs self-assembled quantum dot structure designed to spatially separate and store photo-generated electron-hole pairs. The structure consists of pairs of strain-coupled quantum dots. Separation of electron-hole pairs into the quantum dots and strain-induced quantum dots has been observed using power-dependant photoluminescence and bias-dependent photoluminescence.

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