Charge Transport Properties in CZT DetectorsGrown by the Vertical Bridgman Technique

Great efforts are being presently devoted to thedevelopment of CdTe and CdZnTe detectors for a large varietyof applications, such as medical, industrial, and space research.We present the spectroscopic properties of some CZT crystalsgrown by the standard vertical Bridgman method and by theboron oxide encapsulated vertical Bridgman method, which hasbeen recently implemented at IMEM-CNR (Parma, Italy). Bythis technique the crystal is grown in an open quartz cruciblefully encapsulated by a thin layer of liquid boron oxide. Thismethod prevents contact between the crystal and the cruciblethereby allowing larger single grains with a lower dislocationdensity to be obtained. Several mono-electrode detectors wererealized each with two planar gold contacts. The samples arecharacterized by an active area of about 7 mm x 7 mm andthicknesses ranging from 1 to 2 mm. The charge transportproperties of the detectors have been studied by mobility-lifetime(µt) product measurements, carried out at the EuropeanSynchrotron Radiation Facility (Grenoble) in the PTFconfiguration, where the impinging beam direction is orthogonalto the collecting electric field. We have performed several finescans between the electrodes with a beam spot of 10 µm x10 µmat various energies from 60 keV to 400 keV. In this work wepresent the test results in terms of µt product of both chargecarriers.