Technology development of high purity germanium crystals for radiation detectors

•Complete production chain needed to grow Ge crystals with extreme high purity.•Ge has been purified in a horizontal multi-zone furnace.•2” Ge single crystals were grown in a sophisticated designed Cz-puller.•Crystals are analyzed by means of Hall-effect measurements and Photo-thermal Ionization Spectroscopy.•Dislocation distribution have been evaluated from etch pits.