Dielectric response of wurtzite gallium nitride in the terahertz frequency range

We report on the characterization of the intrinsic, anisotropic, dielectric properties of wurtzite gallium nitride in the spectral range of 0.5-11 THz, using terahertz time-domain spectroscopy. The ordinary (ε˜⊥) and extraordinary (ε˜∥) components of the complex dielectric function were determined experimentally for a semi-insulating, m-plane gallium nitride single crystal, providing measurements of the refractive indices (n⊥,∥) and absorption coefficients (α⊥,∥). These material parameters were successfully modeled by considering the contribution of the optical phonon modes, measured using Raman spectroscopy, to the dielectric function, giving values for the relative static dielectric constants of ε0⊥=9.22±0.02 and ε0∥=10.32±0.03 for wurtzite gallium nitride.