Strain-Tunable Phonon Coupling and Polarization Optoelectronics in Supersaturation-Grown Boron Phosphide Nanowires

Boron phosphide (BP) nanowires represent a rare 1D semiconductor, combining outstanding chemical stability, ultrahigh hardness, and high thermal conductivity. However, their controlled growth and optical functionality remain largely unexplored due to irregular morphologies, toxic precursors, and complex synthesis routes. Here, we develop a supersaturation-engineered chemical vapor transport (CVT) strategy to synthesize air-stable, single-crystalline cubic BP nanowires with tunable diameters. Strain-engineered Raman spectroscopy reveals pronounced phonon broadening and symmetry-selective frequency shifts, uncovering strong strain-phonon coupling. The inherent noncentrosymmetry and nanoscale confinement further induce highly anisotropic Raman and polarization-resolved SHG responses. The BP nanowires show remarkable environmental stability over 12 months and competitive photodetector performance, with a responsivity of 5.2 × 10⁴ A/W and detectivity exceeding 6.4 × 10¹¹ Jones under 595 nm illumination. The device also shows good ambient-storage stability and flexible-substrate compatibility. Integration with MoS₂ amplifies polarization discrimination, achieving an anisotropy ratio of 2.87 at 532 nm, surpassing previously reported low-dimensional systems. This work establishes strain-phonon coupling-mediated polarization control as a new paradigm for BP-based optoelectronic and photonic platforms.