Far-Infrared Optical Properties of Quenched Germanium III. Effects of Additional Impurities

The far-infrared absorption spectra of quenched germanium containing Fe, Ni, Cu, Ag and Au were measured in order to study the effects of these additional impurities on the quenched-in acceptors, and it was found that these impurities perturb the quenched-in acceptors. Particularly, when the crystal was doped with Cu, Ag or Au impurities, only the absorption band series were observed in the wavenumber region around 50 cm-1 where the absorption bands due to the SA1 acceptor of pure quenched germanium were observed. These series were slightly shifted from the bands due to the normal SA1 acceptor. The absorption band series due to the SA1 acceptor were hardly observed in the sample containing Fe impurity, although the bands due to other quenched-in acceptors were observed. These facts seem to contradict the models for the SA1 acceptor proposed so far.