Annealing characteristics of neutron-transmutation-doped germanium

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Abstract
The effects of thermal- and injection-enhanced annealing on the electrical properties of initially high-purity (NA−ND =1010 cm−3) neutron-transmutation-doped (NTD) Ge were investigated using capacitance transient spectroscopy and variable temperature Hall effect. Complete recovery of electrical properties was observed after thermal annealing at 400 °C for 6 h, and significant activation of dopants created by the NTD process is seen even in samples left at ambient temperature for eight months after irradiation. Electric field-enhanced emission of trapped holes from deep level, damage-induced states was used to verify their acceptor nature, and a recombination-enhanced annealing mechanism was observed for several deep acceptors. Other high-purity samples irradiated with a lower dose of fast neutrons only (average energy 4.2 MeV) showed many deep hole traps, most of which were tentatively correlated with the amount of hydrogen in the parent crystal. These deep level damage centers were not observed in the more heavily damaged NTD samples.