Observation of raman scattering by localized optical phonons bound to neutral donors in GaP:Si

Raman scattering by localized optical phonons bound to neutral donors with degenerate ground state has been observed in GaP:Si. The scattering efficiency was measured at T=6.0±0.1 K as a function of the net donor concentration N_D-N_A ranging from 1.6 ·10¹⁷ to 7.1· 10¹⁷ cm^-3. It is found that reasonable agreement with the theory of weakly coupled electron-phonon modes obtained if a Bohr radius of $\text{a}{}_0\text{=5.4}\text{A}\text{?}$ is used, whereas $\text{a}{}_0\text{=7.5}\text{A}\text{?}$ is obtained in the hydrogenic effective-mass approximation using the ionization energy E_D=86.7 meV.