(a) InBi-like vibration modes TO (represented by the red section) and LO (purple section), together with InP-like disorder-activated acoustical modes, which are used for the multi-peak fitting in the low frequency range from 93 cm⁻¹ to 218 cm⁻¹. The intensities of the Raman spectra are multiplied by 15, 3, and 1.5 for x = 0, 0.47%, and 1.47% samples, respectively. (b) The Bi content dependent TO (red solid) and LO (black square) intensity ratio R_Bi (R_Bi = [I(x) − I(0.47%)]/I(0.47%)) for the InP_1−xBi_x sample, and the solid line is for the fitted results.