Leakage current measurements on pixelated CdZnTe detectors

In the field of the R&D of a new generation hard X-ray cameras for space applications we focus on the use of pixelated CdTe or CdZnTe semiconductor detectors. They are covered with 64 (0.9 x 0.9 mm(2)) or 256 (0.5 x 0.5 mm(2)) pixels, surrounded by a guard ring and operate in the energy ranging from several keV to 1 MeV, at temperatures between -20 and +20 degrees C. A critical parameter in the characterisation of these detectors is the leakage current per pixel under polarisation (similar to 50-500 V/mm). In operation mode each pixel will be read-out by an integrated spectroscopy channel of the multi-channel IDeF-X ASIC currently developed in our lab. The design and functionality of the ASIC depends directly on the direction and value of the current. A dedicated and highly insulating electronics circuit is designed to automatically measure the current in each individual pixel, which is in the order of tens of pico-amperes. Leakage current maps of different CdZnTe detectors of 2 and 6mm thick and at various temperatures are presented and discussed. Defect density diagnostics have been performed by calculation of the activation energy of the material. (c) 2006 Elsevier B.V. All rights reserved.