Molecular ground hole state of vertically coupled GeSi/Si self-assembled quantum dots

Abstract

We study the ground state of a hole confined in two vertically coupled GeSi/Si quantum dots as a function of the interdot distance and dot composition within the sp(3) tight-binding approach. Both quantum-mechanical tunneling and inhomogeneous strain distribution are included. For pure Ge dots, the strain is found to have two effects on the hole binding energy: (i) reduction of the binding energy below the value of the single dot with increasing dot separation and (ii) molecular bond breaking for intermediate interdot distances and posterior bond restoration at larger distance. Both effects are smeared upon Ge-Si intermixing.

Increased conductance of individual self-assembled GeSi quantum dots by inter-dot coupling studied by conductive atomic force microscopy

“…BL samples B and D were fabricated by depositing another 2.9 and 3.4 nm Ge on samples of A and C respectively, with a 5 nm Si acting as the spacer layer. In previous studies [13,25], the GeSi QDs separated by a 5 nm Si spacer layer were found to exhibit vertical coupling effects. The topography and current measurements were carried out with a commercial AFM equipment (MultiMode V, Bruker Nano Surfaces Division, Santa Barbara, CA, USA) at room temperature.…”