Self-assembled InAs quantum dots formed by molecular beam epitaxy at low temperature and postgrowth annealing

Self-assembled InAs quantum dots are grown at low temperature (LT) by molecular beam epitaxy (MBE) on GaAs substrates. The growth is in situ monitored by reflection high-energy electron diffraction, and ex situ evaluated by atomic force microscopy for the morphological properties, and by high-resolution x-ray diffraction for the structural properties. While two monolayers as-grown LT (250 °C) InAs layers exhibit shallow mounds due to the low adatom migration length at low temperature, well-developed InAs dots are formed after postgrowth annealing above 450 °C. The structural quality of the LT GaAs matrix grown on top and of the embedded InAs dot layer is improved when a 3 nm GaAs interlayer is deposited (at 480 °C) on the InAs dots and subsequently annealed at 580 °C before LT GaAs overgrowth. These high structural quality LT-grown InAs dots are considered for applications in high-speed optical modulators and switches operating at low power by combining the high optical nonlinearity of quantum dots with t...

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