Laser-Induced Solution-Liquid-Solid Epitaxial Growth of Vertically Aligned Germanium Nanowires

Epitaxial growth of one-dimensional semiconductors provides a compelling route to vertically integrated heterostructure architectures with coherent interfaces and a high crystalline quality. However, vapor-phase approaches are typically constrained by the thermal budget and require complex infrastructure, whereas solution-liquid-solid (SLS) syntheses generally yield colloidal products with compromised crystallinity and limited capability for monolithic integration. Here, we report a laser-induced solution-liquid-solid (laser-SLS) synthesis method that enables epitaxial growth of vertically aligned, single-crystalline germanium (Ge) nanowires, a group-IV semiconductor for advanced electronic applications. Through the use of bismuth (Bi) catalysts in the laser-SLS process, periodically ordered Ge nanowire arrays are obtained with uniform morphology and a well-defined epitaxial relationship with the substrate. Pulsed-laser irradiation provides spatially confined photothermal heating at the catalyst-substrate interface. This localized heating promotes the precursor reaction and sustains rapid nanowire growth, while the surrounding solution remains at a globally low temperature. Electrical measurements show nearly linear current-voltage characteristics with low contact resistance, consistent with a high carrier concentration in the nanowires and an epitaxial nanowire-substrate junction. By enabling epitaxial nanowire growth under low thermal budgets, laser-SLS may provide a viable pathway to mitigate persistent contact challenges in n-type Ge and support opportunities for heterogeneous and monolithic integration in advanced CMOS and nanoelectronic technologies.