Development of planar P-type point contact germanium detectors for low-mass dark matter searches

The detection of low-energy deposition in the range of sub-eV through ionization using germanium (Ge) with a bandgap of similar to 0.7 eV requires internal amplification of the charge signal. This can be achieved through high electric field that accelerates charge carriers, which can then generate more charge carriers. The minimum electric field required to generate internal charge amplification is derived for different temperatures. We report the development of a planar point contact Ge detector in terms of its fabrication and the measurements of its leakage current and capacitance as a function of applied bias voltage. With the determination of the measured depletion voltage, the field distribution is calculated using GeFiCa, which predicts that the required electric field for internal charge amplification can be achieved in proximity to the point contact. The energy response to an Am-241 source is characterized and discussed. We conclude that such a detector with internal charge amplification can be used to search for low-mass dark matter.

Automated summary

This article discusses the development of a germanium detector with internal charge amplification for the search of low-mass dark matter. The fabrication process of the detector is described, and measurements of leakage current and capacitance as a function of applied bias voltage are presented. The calculations predict that the required electric field for internal charge amplification can be achieved near the point contact. The energy response to an Am-241 source is characterized and discussed, and the potential of the detector for low-mass dark matter detection is evaluated.