  A model of the Li-diffused inactive layer in P-type high purity germanium
detectors is built to describe the transportation of charge carriers and
calculate the charge collection efficiency therein. The model is applied to
calculate charge collection efficiency of a P-type point-contact germanium
detector used in rare event physics experiments and validated in another P-type
semi-planar germanium detector. The calculated charge collection efficiency
curves are well consistent with measurements for both detectors. Effects of the
Li doping processes on the charge collection efficiency are discussed based on
the model. This model can be easily extended to other P-type germanium
detectors, for instance, the P-type broad-energy Ge detector, and the P-type
inverted-coaxial point-contact detector.

Instrumentation and Detectors