Large and uniform optical emission shifts in quantum dots externally strained along their growth axis

TL;DR

This paper presents a method for applying and measuring uniform tensile strain on quantum dots along their growth axis, revealing significantly larger optical emission shifts compared to perpendicular stress, with implications for tunable photonic devices.

Contribution

The study introduces a novel technique for applying and calibrating homogeneous strain on quantum dots along their growth axis, enabling direct comparison of strain effects.

Findings

Optical emission shifts are 5-10 times larger under axial strain.

The strain field in the core is homogeneous due to the isotropic shell.

The method allows reliable in situ calibration of strain effects.

Abstract

We introduce a method which enables to directly compare the impact of elastic strain on the optical properties of distinct quantum dots (QDs). Specifically, the QDs are integrated in a cross-section of a semiconductor core wire which is surrounded by an amorphous straining shell. Detailed numerical simulations show that, thanks to the mechanical isotropy of the shell, the strain field in a core section is homogeneous. Furthermore, we use the core material as an in situ strain gauge, yielding reliable values for the emitter energy tuning slope. This calibration technique is applied to self-assembled InAs QDs submitted to incremental tensile strain along their growth axis. In contrast to recent studies conducted on similar QDs stressed perpendicularly to their growth axis, optical spectroscopy reveals 5-10 times larger tuning slopes, with a moderate dispersion. These results highlight the importance of the stress direction to optimise QD response to applied strain, with implications both in static and dynamic regimes. As such, they are in particular relevant for the development of wavelength-tunable single photon sources or hybrid QD opto-mechanical systems.