Electric field reconstruction and transport parameter evaluation in CZT X-ray detectors

The laser-induced current technique has been successful used to reconstruct the spatial profile of the electric field along the thickness of a set of CdZnTe spectroscopic X-ray detectors. Current transient profiles for electrons at different applied voltages have been analyzed by means of a minimization procedure demonstrating its applicability to samples with thickness ranging from 250 μm to 4 mm. Mobility and lifetime of electrons have been also deduced and compared with the mobility-lifetime product, as evaluated by fitting the charge collection efficiency curves under a suitable electric field profile model. Comparison between results from both techniques gives a good agreement and confirms the validity of the procedure. This method results applicable each time that carrier transit times can be evaluated from the laser-induced current transients. It could be suitable for many other devices provided that they are made of materials with sufficiently high resistivity, i.e. with a sufficiently low density of free carriers in dark conditions.