Surface Characterization of P-Type Point Contact Germanium Detectors

Frank Edzards, Lukas Hauertmann, Iris Abt, Chris Gooch, Björn Lehnert, Xiang Liu, Susanne Mertens, David C. Radford, Oliver Schulz, Michael Willers

Research output: Contribution to journalArticlepeer-review

3 Scopus citations


P-type point contact (PPC) germanium detectors are used in rare event and low-background searches, including neutrinoless double beta (0νββ) decay, low-energy nuclear recoils, and coherent elastic neutrino-nucleus scattering. The detectors feature an excellent energy resolution, low detection thresholds down to the sub-keV range, and enhanced background rejection capabilities. However, due to their large passivated surface, separating the signal readout contact from the bias voltage electrode, PPC detectors are susceptible to surface effects such as charge build-up. A profound understanding of their response to surface events is essential. In this work, the response of a PPC detector to alpha and beta particles hitting the passivated surface was investigated in a multi-purpose scanning test stand. It is shown that the passivated surface can accumulate charges resulting in a radial-dependent degradation of the observed event energy. In addition, it is demonstrated that the pulse shapes of surface alpha events show characteristic features which can be used to discriminate against these events.

Original languageEnglish
Pages (from-to)489-511
Number of pages23
Issue number4
StatePublished - Dec 2021
Externally publishedYes


  • P-type point contact germanium detectors
  • alpha and beta surface backgrounds
  • neutrinoless double beta decay


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