Macro- and micro-strain in GaN nanowires on Si(111)

TL;DR

This study investigates the strain distribution in GaN nanowires grown on Si(111), revealing that while the nanowires are strain-free on a macro scale, coalescence induces micro-strain affecting optical properties.

Contribution

It provides a detailed analysis of macro- and micro-strain in GaN nanowires using x-ray diffraction, highlighting the impact of coalescence on micro-strain levels.

Findings

Nanowires are strain-free macroscopically.

Coalescence induces micro-strain of ±0.015% to ±0.03%.

Micro-strain affects photoluminescence linewidth.

Abstract

We analyze the strain state of GaN nanowire ensembles by x-ray diffraction. The nanowires are grown by molecular beam epitaxy on a Si(111) substrate in a self-organized manner. On a macroscopic scale, the nanowires are found to be free of strain. However, coalescence of the nanowires results in micro-strain with a magnitude from +-0.015% to +-0.03%.This micro-strain contributes to the linewidth observed in low-temperature photoluminescence spectra.