Raman scattering in InP doped by Be$^+$-ion implantation

InP (100) crystals implanted with Be$^+$ ions with an energy of 100 keV and doses of 10$^{13}$–10$^{15}$ cm$^{-2}$ are studied by Raman spectroscopy before and after thermal annealing at temperatures of 300–850$^\circ$C. It is found that, as the implanted ion dose is increased, the surface region of InP is partially amorphized; in this case, spectral lines related to longitudinal lattice vibrations exhibit a shift to lower frequencies and inhomogeneous broadening, which is indicative of the formation of a nanocrystalline phase. Thermal annealing results in recovery of the crystal structure of InP. At annealing temperatures of $>$ 700$^\circ$C, scattering at phonon–plasmon coupled modes is detected in the Raman spectra. This is attributed to electrical activation of the impurity. From the frequency of the phonon–plasmon mode, the concentration of heavy holes is estimated in the context of the model of a two-oscillator dielectric function.