Wide-Band Gap Binary Semiconductor P₃N₅ with Highly Anisotropic Optical Linearity and Nonlinearity

Wide-band gap binary semiconductors find extensive use in advanced optoelectronic devices due to their exceptional electronic, optical, and defect properties. This paper systematically investigates the linear and nonlinear optical and defect properties of two P₃N₅ structures as wide-band gap binary semiconductors and evaluates their responses to external pressure modulation using first-principles calculations. The research demonstrates that the high-pressure phase of P₃N₅ has a broad UV solar-blind band gap (E_g ∼ 4.9 eV) and displays highly anisotropic optical linearity and nonlinearity, including a significant second harmonic generation effect (d₂₄ ∼ 1.8 pm/V) and large birefringence (Δn ∼ 0.12), exhibiting a relatively small change in amplitude against pressure due to unique lattice incompressibility. This material enables birefringent phase-matched second harmonic coherent output at a much shorter wavelength (down to 286 nm) than currently known wide-band gap binary semiconductors such as SiC, GaN, AlN, Ga₂O₃, and Si₃N₄. An in-depth study of the defect properties of P₃N₅ in relation to its UV optical properties is also provided. These results are important references for utilizing the optoelectronic functions of this binary material system.