Synthesis and growth of ZnGeP2 crystals: Prevention of non-stoichiometry

Abstract The causes of non-stoichiometry in both synthesis and growth process of ZnGeP 2 (ZGP) have been studied. The effects of mechanical oscillation (MO) and gradient cooling (GC) techniques employed in the synthesis of ZnGeP 2 polycrystals have been investigated. X-Ray Diffraction analysis (XRD) has identified that phosphorus was the main loss component. The growth of ZnGeP 2 crystal was carried out in a three-section vertical Bridgman (VB) furnace. A certain amount of phosphorus was added to ZnGeP 2 polycrystals before growth. The temperature gradients were controlled at 10–15 °C/cm within crystallization zone. A ZnGeP 2 crystal with the size of Φ 25 mm×55 mm was obtained. The proportions of P, Ge and Zn in the grown crystal were measured with Energy Dispersive Spectrometer (EDS). The results showed that the grown crystal has good stoichiometry and homogeneity. Infrared transmittance and absorption spectra show that the crystal has low absorption in 2.0–10.0 μm range. Absorption contour maps by automatic infrared microscope demonstrate that optical homogeneity of grown crystal is good.