  P-type point contact (PPC) germanium detectors are used in rare event and
low-background searches, including neutrinoless double beta (0vbb) 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.

Instrumentation and Detectors;High Energy Physics - Experiment