Nanowires are one-dimensional nanostructures with diameters typically in the range of a few to hundreds of nanometers and lengths that can extend to several micrometers, giving them a very high aspect ratio. Because of their confined geometry, nanowires exhibit unique electrical, optical, and mechanical properties that are significantly different from their bulk counterparts. In semiconductor nanowires such as GaAs, GaAsSb, or Si, quantum confinement and large surface-to-volume ratio strongly influence charge transport, band structure, and light–matter interaction. These properties make nanowires highly attractive for applications in optoelectronics, photodetectors, solar cells, sensors, and nano-bioelectronic devices. Additionally, nanowires can be grown with precise control over composition, doping, and crystal phase using techniques like molecular beam epitaxy (MBE), enabling advanced device engineering at the nanoscale.