Residual strain and piezoelectric effects in passivated GaAs/AlGaAs core-shell nanowires

TL;DR

This study investigates how residual strain and piezoelectric effects influence the optical properties of passivated GaAs/AlGaAs core-shell nanowires, revealing a significant band-edge red shift with increasing shell thickness.

Contribution

It demonstrates the combined impact of strain and piezoelectric fields on band-edge shifts in GaAs/AlGaAs nanowires, supported by experimental observations and theoretical calculations.

Findings

Band-edge red shift up to 14 meV with shell thickness

Tensile strain from AlGaAs shell causes part of the shift

Piezoelectric fields due to Al fluctuations also contribute

Abstract

We observe a systematic red shift of the band-edge of passivated GaAs/Al0.35Ga0.65As core-shell nanowires with increasing shell thickness up to 100 nm. The shift is detected both in emission and absorption experiments, reaching values up to 14 meV for the thickest shell nanowires. Part of this red shift is accounted for by the small tensile strain imposed to the GaAs core by the AlGaAs shell, in line with theoretical calculations. An additional contribution to this red shift arises from axial piezoelectric fields which develop inside the nanowire core due to Al fluctuations in the shell.