Improved photoluminescence efficiency of patterned quantum dots incorporating a dots-in-the-well structure

Correlation between photoluminescence and morphology for single layer self-assembled InGaAs/GaAs quantum dots

Single layer self-assembled InGaAs quantum dots (QDs) are manipulated by using different arsenic species on GaAs (100) surface. The As₄ molecules are experimentally observed to be more promising than As₂ to promote the formation of one-dimensionally-aligned QD-chain arrays. The lateral alignment of QDs and the corresponding formation of dot chains are explained by the anisotropic surface kinetics in combination with the different reactivities of the two molecules with bonding sites on the GaAs (100) surface. Photoluminescence (PL) measurements demonstrate that the spectra of the QD-chains broaden to higher energy and increases in intensity with increasing excitation laser power. The PL band of the QD-chains also exhibits a 9 meV reduction in linewidth as temperature increases starting from 8 K. These observations confirm an efficient lateral coupling between neighboring QDs and thereafter polarized QD emission, whereas the randomly distributed QDs grown with As₂ show no preferential polarization. Such QD-chains exhibiting anisotropic properties have the potential for nanophotonics applications like electro-optic modulators with very low drive voltage and ultra-wide bandwidth operation.

Carrier dynamics in InAs/AlAs quantum dots: lack in carrier transfer from wetting layer to quantum dots

Structures with self-assembled InAs quantum dots (QDs) embedded in an AlAs matrix have been studied by steady-state and transient photoluminescence. It has been shown that in contrast to InAs/GaAs QD systems carriers are mainly captured by quantum dots directly from the AlAs matrix, while transfer of carriers captured by the wetting layer far away from QDs to the QDs is suppressed. At low temperatures the carriers captured by the wetting layer are localized by potential fluctuations at the wetting layer interface, while at high temperatures the carriers are delocalized but captured by nonradiative centers located in the wetting layer.

Fabrication and characteristics of broad-area light-emitting diode based on nanopatterned quantum dots

The device fabrication and integration of nanopatterned quantum dots (PQDs) are realized through the demonstration of a broad-area light-emitting diode with PQD active region. The device involves two growth processes, first to form PQDs by selective-area epitaxy on an SiO(2) mask and then to complete the device structure after mask removal. Linear current-voltage characteristics are observed with sharp turn-on, low leakage current and low forward resistance. Electroluminescence spectra show PQD intraband structure and low quenching of emission from 77 K to room temperature. Light-current measurements demonstrate external quantum efficiency per PQD comparable to self-assembled QDs, thus providing a possible route toward individually addressable single QD devices.