Localization of Holes in an InAs∕GaAs Quantum-Dot Molecule

Abstract

Deep-level transient spectroscopy is used to study the emission of holes from the states of a vertically coupled system of InAs quantum dots in p-n InAs/GaAs heterostructures. This emission was considered in relation to the thickness of a GaAs interlayer between two layers of InAs quantum dots and to the reversebias voltage Ur. It is established that hole localization at one of the quantum dots is observed for a quantum-dot molecule composed of two vertically coupled self-organized quantum dots in an InAS/GaAs heterostructure that has a 20-A-thick or 40-A-thick GaAs interlayer between two layers of InAs quantum dots. For a thickness of the GaAs interlayer equal to 100 A, it is found that the two layers of quantum dots are incompletely coupled, which results in a redistribution of the hole localization between the upper and lower quantum dots as the voltage Ur applied to the structure is varied. The studied structures with vertically coupled quantum dots were grown by molecular-beam epitaxy using self-organization effects.