  The charge collection properties in different particle sensor materials with
respect to the shape of the generated signals, the electric field within the
detector, the charge carrier mobility and the carrier lifetime are studied with
the transient current technique (TCT). Using the well-known properties of Si as
a reference, the focus is laid on Cadmium-Telluride (CdTe) and
Cadmium-Zinc-Telluride (CZT), which are currently considered as promising
candidates for the efficient detection of X-rays. All measurements are based on
a transient-current technique (TCT) setup, which allows the recording of
current pulses generated by an 241Am alpha-source. These signals will be
interpreted with respect to the build-up of space-charges inside the detector
material and the subsequent deformation of the electric field. Additionally the
influence of different electrode materials (i.e. ohmic or Schottky contacts) on
the current pulse shapes will be treated in the case of CdTe. Finally, the
effects of polarization, i.e. the time-dependent degradation of the detector
signals due to the accumulation of fixed charges within the sensor, are
presented.
