Mg- and Bi-Nanoparticle-Mediated Growth of InP Nanowires

Replacing Au catalysts in III−V nanowire growth is critical for clean, CMOS-compatible nanophotonics. Here, we explore a gold-free route using magnesium and bismuth nanoparticles as mediators. The nanoparticles were synthesized by laser ablation and deposited on gallium arsenide (100) substrates prior to nanowire growth by chemical beam epitaxy. An untreated reference substrate subjected to the same growth procedure produced no nanowires, whereas both nanoparticle pretreatments promoted nanowire formation within the investigated process window. By systematically varying the trimethylindium flow and growth temperature, we found that both magnesium and bismuth influence nanowire morphology and growth behavior, while their distinct temperature-dependent growth rates indicate different interfacial kinetics. Energy-dispersive X-ray spectroscopy did not resolve localized Mg or Bi signals at the nanowire tips, whereas weak signals from the corresponding pretreatment elements were detected in the larger In-rich particles located along the nanowire sidewalls, indicating a spatially nonuniform post-growth distribution. Low-temperature photoluminescence nevertheless revealed distinct optical responses for the Mg- and Bi-pretreated samples, indicating that the two pretreatments produce different defect and recombination landscapes. Electron microscopy revealed balloon-like InP apex regions capped by In-rich, P-depleted hemispherical particles, particularly at higher temperatures, as well as In-rich particles along the nanowire sidewalls. These features are consistent with the redistribution and dewetting of In near growth termination and during vacuum cooldown. High Resolution Transmission Electron Microscopy and electron diffraction further showed that the nanowires remained predominantly wurtzite throughout both type of mediators. These results support a seed-mediated, In-assisted pathway in which magnesium and bismuth promote nanowire nucleation and establish distinct surface and interfacial conditions. This study demonstrates the potential of group-II and group-V nanoparticle pretreatments for the controlled, gold-free growth of indium phosphide nanowires.