Spectroscopic Response and Charge Transport Properties of CdZnTe Detectors Grown by the Vertical Bridgman Technique

In this work, we present the results of spectroscopic investigations on CdZnTe (CZT) detectors grown by the boron oxide encapsulated vertical Bridgman technique (1MEM-CNR, Parma, Italy). The detectors, with different thicknesses (1 and 2.5 mm), are characterized by the same electrode layout (gold electroless contacts): the anode is a central electrode (2 x 2 mm(2)) surrounded by a guard-ring electrode, while the cathode is a planar electrode covering the detector surface (4.1 x 4.1 mm(2)). The results of electrical investigations point out the low leakage currents of these detectors even at high bias voltages: 38 nA/cm(2) (T = 25 degrees C) at 10000 V/cm. The time stability and the spectroscopic response of the detectors, at different temperatures and fluxes, were investigated. Am-241 spectra were measured up to 1 Mcps. The detectors were compared with the traveling heater method (THM) CZT grown detectors (Redlen), fabricated with the same electrode layout. These activities are in the framework of an Italian research project on the development of energy resolved photon counting (ERPC) systems for high flux energy resolved X-ray imaging.