Investigation of a contacting scheme for self-assembled cleaved edge overgrown InAs nanowires and quantum dot arrays

Abstract

The expanding of research in nano-scale systems is essentially driven by interest in the fun-damental physical properties of solid state matter at the nanoscale and the hope to apply them to novel technologi-cal devices. With self-assembled (bottom-up approach) nanostructures it is possible to achieve even smaller sized structures in combination with top-down technologies and allow at the same time a high control of the size distribu-tion. An example for such materials are defect free semi-conductor QDs grown by MBE or CVD processes [1]. Es-pecially III–V self-assembled QDs, e.g. InGaAs QDs, are subject to intense investigations due to their superior opti-cal properties. These systems are interesting due to promis-ing applications, like single photon sources, lasing, optical amplifiers or solar cells [2–4]. For this reason it is interest-ing to characterize the electronic properties of self-assembled nanostructures. Ensembles of QDs can be con-tacted by embedding the QDs film into a pin-diode struc-ture. However to address single or a small ensemble of nanostructures still represents a challenging task. In several previous publications the promising approach of self-assembled InAs nanostructures obtained by cleaved edge overgrowth was presented [5, 6]. Again the optical proper-ties are easily accessible [7], but for further investigations a direct injection of charge carriers into the nanostructures is interesting. Previous pioneering work has shown how CEO structures can be used for low-dimensional transport at the cleavage plane first in GaAs quantum wires [8] and more recently in AlAs quantum wires [9]. At this point we would like to shortly review the technique of self-assembled InAs nanostructure growth. The procedure re-lies on the fact that the three-dimensional InAs layer