Degree of Copper Contamination in Germanium Heat-Treated at High Temperatures

The degree of copper contamination in Ge heat-treated above 700 °C is studied by measuring the density of the copper levels in order to provide an experimental standard which serves to treat Ge at high temperatures. The degree of contamination is in the range 1013 to 1016 cm−3, depending upon the heat-treatment methods and the purity of water used to rinse specimens before the heat treatments. Joule heating in a vacuum attains the lowest degree of contamination, 2 × 1013 cm−3, above 900 °C. The results warn us to take into account the presence of an appreciable number of Cu atoms whenever thermally induced defects, impurity diffusion or precipitation, and dislocations are studied.