Self-organizing growth of erbium arsenide quantum dots and wires in gallium arsenide by molecular beam epitaxy

Abstract
Gallium arsenide doped with erbium has been grown by molecular beam epitaxy. At growth temperatures in the range 540–605 °C, and with arsenic to gallium flux ratios of 2 and more, the erbium forms uniform crystalline microprecipitates of ErAs when the concentration exceeds 7×1017 cm−3. The diameter can be varied in the range 11–21 Å by altering the growth temperature. Reducing the arsenic to gallium flux ratio to close to stoichiometry changes the growth mode to one yielding quantum wires aligned in the growth direction. Subtle changes in growth conditions lead to bifurcated structures, which we refer to as quantum trees.