Infra-red Investigation of the Acceptor Levels Formed by Copper in Germanium

Infra-red absorption measurements from 1 to 34 μ have been made on germanium containing varying amounts of antimony and copper at temperatures down to 20°K. The results indicate that the three acceptor levels introduced by copper into germanium can be identified by their effect on the low temperature absorption spectra of suitably doped samples. The appearance of the levels is in good agreement with the existing theory, and in addition to this, an excited state of the shallow acceptor level has been identified which has not been previously reported.