Investigation of response behavior in CdTe detectors versus inter-electrode charge formation position

Some important features of semiconductor detectors (pulse height, energy resolution, photopeak efficiency) are strongly affected by charge collection efficiency; therefore low charge mobility and trapping/detrapping phenomena can more or less degrade the CdTe based detectors performance, depending on the distance between the charge formation location and the collecting electrodes. Using a narrow photon beam, obtained by a 20 mm thick tungsten collimator, the author has studied the response of a small sample of CdTe(Cl) planar detectors. In particular the authors have investigated the behavior of the above parameters vs. the change formation position induced by the incoming radiation irradiating the detectors perpendicularly to the electric field and performing a fine scanning of the inter-electrode region. For comparison the detectors were irradiated also with a non collimated beam both perpendicularly and in the classical configuration (through the cathode)