Characterization of Pure Germanium for Detector Fabrication

Germanium crystals grown in wet H2 from material that contains trace amounts of silicon exhibit "smooth pits" in addition to familiar dislocation pits seen on etched surfaces. Such material appears normal by the usual methods of electrical evaluation, but detectors fabricated from it invariably exhibit severe trapping. Experiments yielding information about the presence of oxygen and silicon in germanium are reported. Preliminary observations indicate that a test for the presence of smooth pits may also provide a critical means for evaluating Li drift material. Examination of a sample of "good" Li drift germanium showed it to be free of these pits, whereas a sample described as, "Drifts normally, but detectors show severe hole trapping." was found to have 700/cm2 smooth pits.