DLTS Study of plastically deformed copper-doped $n$-type germanium

Classical deep level transient spectroscopy (DLTS) and its modification are used to study the time constants of electron capture by substitutional Cu$_s^{2-}$ atoms and thermal electron emission from Cu$_s^{3-}$ atoms in plastically deformed Cu-doped $n$-type germanium. The activation energy $E_\sigma$, the electron capture cross-section, the energy $E_3$ of the third acceptor level of Cu$_s^{3-}$ atoms, and the ionization entropy are determined. The lack of $E_3$-level broadening, the exponential capture kinetics for a filling-pulse duration of $t_p\lesssim$ 1 ms, the fact that the Cu$_s^{2-/3-}$-atom recombination parameters are independent of the dislocation density, and the low concentration of Cu$_s^{2-/3-}$ atoms in the deformed samples suggest that the DLTS spectra are due to Cu$_s^{2-/3-}$ atoms located outside the Read cylinders.