Zinc germanium diphosphide (ZGP) crystals (15 mm in diameter and 65 mm in length) were successfully grown by the modified vertical Bridgman method on seeds at different pulling rates (0.5 mm/h and 0.75 mm/h) in order to study the defect generation during crystal growth. At the different positions (the onset, middle and end) in single crystals, their properties of ZGP crystals were investigated by X-ray diffraction, etching technique and optical transmission spectra. The results indicate that the increase in the pulling rate deteriorates the crystal quality at the onset part of the single crystals. The etch pit density (EPD) and the full width at half maximum (FWHM) of the X-ray rocking curves increase, while the optical transmittance decreases with increasing pulling rate. However, the increase in the pulling rate hardly influences the crystal quality at the middle and end part of the single crystals. (C) 2016 Elsevier B.V. All rights reserved.