Deep levels, associated with misfit dislocations in "clean" and copper contaminated p-type Si/Si_0.98Ge_0.02/Si structures, are under consideration. In the as-grown (non-contaminated) samples dislocations were found to exhibit a very low recombination activity, detectable with the electron-beam-induced current technique only at low temperatures. Deep-level-transient spectroscopy revealed a dislocation-related hole trap level at E_t = E_v + 0.2 eV which was identified as band-like. The position of the observed level is close to the theoretically predicted hole trap state of the intrinsic stacking fault between a dissociated dislocation. Contamination with a low copper concentration (5 ppb) gave rise to a large increase of the recombination activity of the dislocations and to the appearance of another dislocation-related defect level at E_t= E_v+ 0.32 eV. Hydrogenation of the copper contaminated sample by a treatment with an acid solution and subsequent reverse-bias anneal at 380 K resulted in the evolution of the levels of substitutional copper and its complexes with hydrogen.