Deep level transient spectroscopy of transition metal impurities in germanium

The n- and p-type germanium wafers have been implanted with Ti, Cr, Fe and Co and the electronic defect levels have been studied by deep level transient spectroscopy (DLTS). Distinct spectra with two to four levels have been observed which are assigned to multiple-acceptor states of the substitutional metal impurities, with, in addition, a deep donor level in the case of Cr and Co. Thermally activated capture cross-sections are observed for the electron traps, in agreement with this assignment. For Fe and Co the DLTS results confirm earlier Hall-effect data, while for Ti and Cr a reliable deep level spectrum has been obtained for the first time.