Suppression of axial growth by boron incorporation in GaAs nanowires grown by self-catalyzed molecular beam epitaxy

Suzanne Lancaster,Werner Schrenk,Heiko Groiss,Tobias Zederbauer,Aaron M Andrews,Donald Macfarland,Gottfried Strasser,Hermann Detz

doi:10.1088/1361-6528/aaf11e

Abstract

The addition of boron to GaAs nanowires grown by self-catalyzed molecular beam epitaxy was found to have a strong effect on the nanowire morphology, with axial growth greatly reduced as the nominal boron concentration was increased. Transmission electron microscopy measurements show that the Ga catalyst droplet was unintentionally consumed during growth. Concurrent radial growth, a rough surface morphology and tapering of nanowires grown under boron flux suggest that this droplet consumption is due to reduced Ga adatom diffusion on the nanowire sidewalls in the presence of boron. Modelling of the nanowire growth puts the diffusion length of Ga adatoms under boron flux at around 700–1000 nm. Analyses of the nanowire surfaces show regions of high boron concentration, indicating the surfactant nature of boron in GaAs.

Highlights

Heterostructured nanowires (NWs) offer interesting prospects as the key building blocks of future electronic and optoelectronic devices
Assuming a linear growth rate starting from 15 mins of growth, we can estimate that the length of the GaAs stems after 18 minutes of growth should be ∼ 960nm
We have observed a strong impact of boron on the morphology of GaAs nanowires grown by solid-source molecular beam epitaxy (MBE)

Summary

Introduction

Heterostructured nanowires (NWs) offer interesting prospects as the key building blocks of future electronic and optoelectronic devices. Bottom-up III-V NWs such as GaAs offer the advantages of a direct bandgap, and the possibility of growing heterostructures both radially [1] and axially [2], while still relying on established processing technology. Investigating strain in nanowires is interesting for the design of radial heterostructures. In order to induce strain in a GaAs nanowire, ternary alloys with two group III or group V elements can be used. While alloys with larger lattice constants than GaAs, such as InxGa1−xAs, are well-researched, few traditional III-As candidates exist with a smaller lattice constant than GaAs. The addition of N to GaAs nanowires has been demonstrated in radial GaAs/GaAs1−yNy heterostructures [7], which leads to Sample

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Results & Discussion

Modelling of adatom diffusion length under B flux

Radial overgrowth of AlGaAs

Conclusion