The optical properties of Zn doped GaP single crystals were investigated in
the spectral range of 200–2500 nm. It was found that the spectral
distributions of R, n, $\varepsilon_{1}$ reflect sharp structure due to
valance conduction band transitions (Eg, E0, E1 and E2)
having the energies 2.17, 2.706, 3.708 and 5.245 eV, respectively. The
tested samples exhibit indirect allowed optical transition associated with
two phonons of energies 24.5 and, 58.7 meV. The free carrier concentration
was found to be 2.11 × 1018 cm−3. The oscillation energy
Eosc, dispersion energy Ed, lattice dielectric constant
$\varepsilon_{L}$, and optical dielectric constant at infinite frequency
$\varepsilon_{\infty}$ were, also, calculated and found to be the values
4.4 eV, 38 eV, 10.27 and 9.7, respectively.