Impurity complex formation in ultra-pure germanium

Several unknown, hydrogenic acceptors and donors were recently discovered in ultra-pure germanium by photoelectric spectroscopy. These centers are not created by elemental impurities. Comparative analysis of a large number of crystals grown under various conditions lead to the conclusion that copper, a fast diffusing multivalent acceptor, together with lithium and/or hydrogen, is responsible for several of the unknown centers. This is the first time that hydrogen has been recognized as playing the role of a donor pairing with an acceptor. Hall effect measurements complementing the photoelectric spectroscopy results lead to a tentative assignment of the following energy levels: (Cu, Li) complexes: E/sub V/ + 20.5 meV/super */, E/sub V/ + 25.0 meV/super */, E/sub V/ + 275 meV(/super */hydrogenic acceptor); (Cu, H) complexes: E/sub V/ + 17.0 meV/super */, E/sub V/ + 17.5 meV/super */, E/sub V/ + 175 meV. Experiments which may help determine the structure of the complexes are proposed