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Carrier transport and electron-lattice interactions of nonlinear optical crystals CdGeP$_2$, ZnGeP$_2$ and CdSiP$_2$

Terahertz time-domain spectroscopy is employed to investigate temperature-dependent properties of bulk chalcopyrite crystals (CdGeP$_2$, ZnGeP$_2$ and CdSiP$_2$). The complex spectra provide the refraction and absorption as a function of temperature, from which electron-phonon coupling and average phonon energies are extracted and linked to the mechanics of the A- and B-site cations. Also, AC conductivity spectra provide carrier densities and electron scattering times, the temperature dependence of which is associated with unintentional shallow dopants. Temperature dependence of the scattering time is converted into carrier mobility and modeled with microscopic transport mechanisms such as polar optical phonon, acoustic phonons, deformation potential, ionized impurity and dislocation scattering. Hence, analysis links the THz optical and electronic properties to relate microscopic carrier transport and carrier-lattice interactions.