  The p-type point-contact germanium detectors have been adopted for light dark
matter WIMP searches and the studies of low energy neutrino physics. These
detectors exhibit anomalous behavior to events located at the surface layer.
The previous spectral shape method to identify these surface events from the
bulk signals relies on spectral shape assumptions and the use of external
calibration sources. We report an improved method in separating them by taking
the ratios among different categories of in situ event samples as calibration
sources. Data from CDEX-1 and TEXONO experiments are re-examined using the
ratio method. Results are shown to be consistent with the spectral shape
method.
