XRD Evaluation of Wurtzite Phase in MBE Grown Self-Catalyzed GaP Nanowires.

Olga Yu Koval,Demid A Kirilenko,Alexey D Bolshakov,Georgiy A Sapunov,Vladimir V Fedorov,Roman G Burkovsky,Sergey V Fedina,Stanislav A Udovenko,Ivan S Mukhin,Liliia N Dvoretckaia,Igor E Eliseev

doi:10.3390/nano11040960

Olga Yu Koval, Demid A Kirilenko + Show 9 more

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https://doi.org/10.3390/nano11040960

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Abstract

Control and analysis of the crystal phase in semiconductor nanowires are of high importance due to the new possibilities for strain and band gap engineering for advanced nanoelectronic and nanophotonic devices. In this letter, we report the growth of the self-catalyzed GaP nanowires with a high concentration of wurtzite phase by molecular beam epitaxy on Si (111) and investigate their crystallinity. Varying the growth temperature and V/III flux ratio, we obtained wurtzite polytype segments with thicknesses in the range from several tens to 500 nm, which demonstrates the high potential of the phase bandgap engineering with highly crystalline self-catalyzed phosphide nanowires. The formation of rotational twins and wurtzite polymorph in vertical nanowires was observed through complex approach based on transmission electron microscopy, powder X-ray diffraction, and reciprocal space mapping. The phase composition, volume fraction of the crystalline phases, and wurtzite GaP lattice parameters were analyzed for the nanowires detached from the substrate. It is shown that the wurtzite phase formation occurs only in the vertically-oriented nanowires during vapor-liquid-solid growth, while the wurtzite phase is absent in GaP islands parasitically grown via the vapor-solid mechanism. The proposed approach can be used for the quantitative evaluation of the mean volume fraction of polytypic phase segments in heterostructured nanowires that are highly desirable for the optimization of growth technologies.

Highlights

Crystal phase engineering in semiconductor nanostructures provides a new design strategy for optoelectronic functional materials with a desired band structure
We propose a complex approach unveiling the influence of the growth parameters on the crystal structure of self-catalytic molecular beam epitaxy (MBE)-grown gallium phosphide (GaP) NWs
Group-III flux was kept constant during the NW growth and was equivalent to the 200 nm/h growth rate of planar GaP/Si(001), corresponding to the Ga beam equivalent pressure (BEP) of 7 × 10−8 Torr

Summary

Introduction

Crystal phase engineering in semiconductor nanostructures provides a new design strategy for optoelectronic functional materials with a desired band structure. This can significantly improve the device performance and functionality produced by the absence of the heterointerface interdiffusion problem and consecutive sharp crystal phase boundaries in crystal-phase heterostructures [1,2]. Nanomaterials 2021, 11, 960 recombination losses [6,7]. H, it was theoretically predicted and shortly after, demonstrated experimentally that GaP becomes a pseudo-direct bandgap material in hexagonal wurtzite (WZ) crystal phase [8,9,10]

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