  High-purity germanium (HPGe) crystals are required to be well-characterized
before being fabricated into Ge detectors. The characterization of HPGe
crystals is often performed with the Hall Effect system, which measures the
carrier concentration, the Hall mobility, and the electrical resistivity. The
reported values have a strong dependence on the size of the ohmic contacts and
the geometry of the samples used in conducting the Hall Effect measurements. We
conduct a systematic study using four samples cut from the same location in a
HPGe crystal made into different sized ohmic contacts or different geometries
to study the variation of the measured parameters from the Hall Effect system.
The results are compared to the C-V measurements provided by the Ge detector
made from the same crystal. We report the systematic errors involved with the
Hall Effect system and find a reliable technique that minimizes the systematic
error to be only a few percent from the Hall Effect measurements.
