(a) Raman spectra between 280 cm⁻¹ and 365 cm⁻¹ with different Bi doping levels, where the dark yellow dots are the experimental data. InP-like TO(L) (green line), LOPC (red line), and TO(Γ) (purple line) modes are used to fit the spectra between 280 cm⁻¹ and 325 cm⁻¹, and LO(L) (blue line) and LO(Γ) (magneta line) modes are used to fit the spectra between 325 cm⁻¹ and 365 cm⁻¹. Navy lines are the fitted curves. (b) Comparison of the Raman spectra in the range from 270 cm⁻¹ to 330 cm⁻¹ between the Z(XX)Z̅ and Z(XY)Z̅ polarized configurations, for samples with x = 0.47% and 1.47%. (c) Bi content-dependent intensities of the LOPC and the corresponding electron concentrations for samples with Bi composition x ≤ 2.23%. (d) The Bi doping content-dependent shifts of the Raman frequencies of LO(L) and LO(Γ) modes. (e) The Bi composition-dependent full width at half maximum (FWHM) of LO(Γ). The black dots represent the experimental data, while the red line guides the eye.