# Correlated nanoscale analysis of the emission from wurtzite versus zincblende (In,Ga)As/GaAs nanowire core-shell quantum wells

## TL;DR

This study investigates how the crystal structure (wurtzite vs. zincblende) affects the emission properties of (In,Ga)As/GaAs nanowire quantum wells using advanced spatially-resolved techniques, revealing a significant emission energy shift due to compositional and strain differences.

## Contribution

It provides the first detailed correlation of crystal polytype effects on quantum well emission using combined hyperspectral imaging, x-ray diffraction, and atom probe tomography.

## Key findings

- Wurtzite segments show a 75 meV blueshift in emission energy.
- A 30% decrease in In mole fraction from zincblende to wurtzite segments.
- Strain effects significantly influence hole ground state energies.

## Abstract

While the properties of wurtzite GaAs have been extensively studied during the past decade, little is known about the influence of the crystal polytype on ternary (In,Ga)As quantum well structures. We address this question with a unique combination of correlated, spatially-resolved measurement techniques on core-shell nanowires that contain extended segments of both the zincblende and wurtzite polytypes. Cathodoluminescence hyperspectral imaging reveals a blueshift of the quantum well emission energy by $75\pm15$ meV in the wurtzite polytype segment. Nanoprobe x-ray diffraction and atom probe tomography enable $\mathbf{k}\cdot\mathbf{p}$ calculations for the specific sample geometry to reveal two comparable contributions to this shift. First, there is a 30% drop in In mole fraction going from the zincblende to the wurtzite segment. Second, the quantum well is under compressive strain, which has a much stronger impact on the hole ground state in the wurtzite than in the zincblende segment. Our results highlight the role of the crystal structure in tuning the emission of (In,Ga)As quantum wells and pave the way to exploit the possibilities of three-dimensional bandgap engineering in core-shell nanowire heterostructures. At the same time, we have demonstrated an advanced characterization toolkit for the investigation of semiconductor nanostructures.