Chemical Impurities and Lattice Defects in High-Purity Germanium

The electrically active impurities remaining in high-purity germanium have been identified by means of far infrared photo-conductivity measurements. The principal donor is phosphorus, often accompanied by lithium and another donor which is believed to be the LiO+ complex. The acceptors present in undoped crystals are boron and aluminum. The tip ends of germanium crystals were examined by mass spectrograph, electron microprobe, and emission spectrograph analyses in a search for the possible presence of unsuspected impurities. The principal elements found were Ag in a first generation crystal and In when traces of this element had been intentionally added. Lattice defects have been studied by means of low temperature annealing and quenching experiments. Acceptor defects found in as-grown crystals can be eliminated by annealing. Two other defects which anneal in the 20-160°C range are found in quenched samples.