3D Strain Imaging of a Heterostructured GaInP/InP Nanowire Using Bragg Coherent Diffraction X-ray Imaging: Implications for Optoelectronic Devices

TL;DR

This study uses advanced X-ray imaging to map strain in a nanowire, showing how it can help design better optoelectronic devices.

Contribution

The study demonstrates 3D strain imaging in a GaInP/InP nanowire using BCDI with high spatial resolution.

Findings

3D strain distribution in an InP segment of a nanowire was imaged with 14 nm resolution.

Measured strain magnitude suggests a higher Ga composition than expected.

Nanowire can accommodate lattice mismatch without exceeding coherency limits.

Abstract

Imaging the strain in nanoscale heterostructures is challenging
since it requires a combination of high strain sensitivity and spatial
resolution. Here, we show that three-dimensional (3D) Bragg coherent
diffraction imaging (BCDI) can be used to image the strain in a single
InP segment within an axially heterostructured GaInP–InP nanowire.
We use a 350 nm-diameter X-ray beam, which is smaller than the nanowire
but larger than the 180 nm long InP segment. The intense nanofocused
beam induced angular distortions, but these are successfully removed
by a correction algorithm. Additionally, we show that data from multiple
scans can be merged despite scan-to-scan variations. The reconstruction
of the merged data set has a spatial resolution of approximately 14
nm, revealing the 3D morphology of the InP segment and its internal
strain distribution. The measured strain shows qualitative agreement
with finite element method simulations, but with slightly larger magnitude,
which indicates a higher Ga composition than the nominal value. The
3D strain map suggests that the nanowire can accommodate the theoretically
predicted lattice mismatch without exceeding the coherency limit.
Continued development of robust BCDI measurements and reconstructions
enables future studies of strain fields and coherency limits in axial
nanowire heterostructures, which are critical for designing next-generation
optoelectronic devices.

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