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Laplace Transform Spectroscopy Studies of Radiation Induced Defects in Germanium

Results of deep level transient spectroscopy (DLTS), Laplace transform DLTS and Laplace transform DLTS combined with the uniaxial stress measurements of electrically active defects induced in Sb-doped germanium crystals by fast neutrons and subsequent annealing are presented in this work. We have used fast neutrons in order to produce uniformly distributed damage, and flux densities in order to produce mainly small clusters of defects. In Ge samples irradiated with low fluences of neutrons the second acceptor level of the Sb-V pair was the dominant electron trap. It is suggested that upon annealing of neutron-irradiated samples Sb-V pairs can interact with Sb atoms, which leads to the formation of the Sb2-V complexes. The Sb2-V complexes have acceptor level in the lower half of the gap (hole trap). Furthermore, we have studied the radiation induced defects in Ge crystals with Laplace DLTS under uniaxial stress. The stress-induced electronic level splitting pattern can provide information regarding the symmetry of a defect complex. We have shown that the most important and dominant electrically active defect in Ge, Sb-V pair, has a trigonal symmetry.

defects; germanium; neutron irradiation; dlts

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