Optical and vibrational properties of the chalcopyrite CdGeP2

We grew CdGeP2 single crystals by using the horizontal Bridgman method. The oscillating transmission spectra of polarized light at various sample temperatures and the Raman shift as function of pressure were observed, and the difference in the refractive index near energy band gap and the Biot dispersion of CdGeP2 as functions of temperature were determined. In the temperature range between room temperature and near 100 K, in which the thermal expansion effect is dominant, the temperature coefficient of the optical energy band gap is given by dE(g,op)/dT = -4.95 x 10(-4) eV/K. The Biot dispersion varied linearly within the temperature in the range between 100 K and 250 K, and the linear coefficient of the Biot dispersion in that temperature range was about 1.61 x 10(-5) rad-mum. We measured the Raman shift under pressure. The linear pressure coefficient of the Raman modes in CdGeP2 could be divided roughly into three groups according to its magnitude.