Abstract Deep level transient spectroscopy has been used to investigate the electrical properties of deep defect states in γ-ray irradiated Ge doped with the isoelectronic elements Pb or Sn. Three deep levels are observed in the irradiated Pb-doped Ge (Ev +0.28 eV, Ec −0.33 eV, Ec −0.39 eV) and two deep levels observed in the Sn-doped Ge (Ev + 0.19 eV, Ec −0.15 eV). For the same γ-ray irradiation doses, Ge crystals grown from graphite crucibles and doped with Pb or Sn shows about two-thirds the total density of deep level defects observed in undoped Ge grown from synthetic quartz crucibles. All of the defect states observed were removed by a 1 hour, 250°C thermal anneal, and all but the Ec −0.39 eV state in the Pb-doped material were neutralized by exposure to a low pressure atomic hydrogen plasma.