Copper in ultra-pure germanium: determination of the electrically active fraction

This paper reports direct measurement of the total Cu concentration and its electrically active fraction in ultra-pure Ge crystals. The fraction of electrically active Cu atoms is shown to be 3*10-3 in hydrogen-grown Ge and 3*10-2 in vacuum-grown Ge. The state of Cu in ultra-pure Ge crystals and the passivation of electrically active Cu-related centres by hydrogen are discussed.