Direct evidence of enhanced Ga interdiffusion in InAs vertically aligned free-standing nanowires

TL;DR

This study provides direct evidence of significant Ga interdiffusion in InAs nanowires grown by molecular beam epitaxy, revealing composition changes and growth mechanisms distinct from typical vapor-liquid-solid methods.

Contribution

It introduces experimental evidence and a growth model that accounts for Ga interdiffusion in InAs nanowires, enhancing understanding of heteroepitaxial nanowire growth processes.

Findings

InAs nanowires are composed of In0.86Ga0.14As.

Nanowires form via diffusion-induced growth with substrate interdiffusion.

The growth model applies broadly to III-V nanowire heteroepitaxy.

Abstract

We present direct evidence of enhanced Ga interdiffusion in InAs free-standing nanowires grown at moderate temperatures by molecular beam epitaxy on GaAs (111)B. Scanning electron microscopy together with X-ray diffraction measurements in coplanar and grazing incidence geometries show that nominally grown InAs NWs are actually made of In$_{0.86}$Ga$_{0.14}$As. Unlike typical vapor-liquid-solid growth, these nanowires are formed by diffusion-induced growth combined with strong interdiffusion from substrate material. Based on the experimental results, a simple nanowire growth model accounting for the Ga interdiffusion is also presented. This growth model could be generally applicable to the molecular beam heteroepitaxy of III-V nanowires.