Monovacancy–As complexes in proton-irradiated Ge studied by positron lifetime spectroscopy

Abstract

We applied positron annihilation lifetime spectroscopy to study the proton-irradiation-induced defects in germanium and its annealing behavior. The n-doped Ge ([As]=9×1017cm−3) samples were irradiated at room temperature with a proton energy of 15MeV at a dose of 1015cm−2. We distinguished a complex containing a vacancy and arsenic atoms. In addition, we observed shallow positron traps, which are ascribed to the impurities in a Ge lattice crystal. Isochronal annealing experiments were carried out in the temperature interval 300–820K. Temperature-dependent positron lifetime measurements were performed after each annealing step. During isochronal annealing of the proton-irradiated Ge, a vacancy–As complex was found to dissociate to its constituents and the single monovacancies eventually anneal out. Two annealing stages were observed: the first, at ∼450K, was attributed to the dissociation of complexes and the second annealing stage, at 650K, was assigned to annealing of vacancies. Shallow positron traps anneal in the temperature range 540–660K.