Electron states, phonon-assisted relaxation and tunneling in self-assembled quantum dot molecules in an electric field

TL;DR

This paper provides a detailed theoretical analysis of phonon-assisted relaxation and tunneling in vertically stacked quantum dot molecules under electric fields, highlighting the conditions for rapid relaxation.

Contribution

It introduces a realistic model accounting for geometry and strain, and calculates relaxation rates considering external electric fields and dot sizes.

Findings

Relaxation times can be as low as 1 ps.

Efficient relaxation requires finely tuned quantum dot structures.

Relaxation rates depend on electric field and geometric parameters.

Abstract

We present a theoretical analysis of the phonon-assisted relaxation in a system composed of two self-assembled vertically stacked quantum dots. We construct realistic model, which takes into account the geometry and strain distribution in the system. We calculate phonon-assisted relaxation rates between the two lowest states (in one- and two-electron cases). The relaxation rates and energy levels are studied as a function of external (axial) electric field and geometry of the structure (dot sizes). We show that the relaxation times can be as low as 1~ps but efficent relaxation occurs only for very finely tuned dots.