Charge Collecting Properties of Proton Irradiated CdTe Detectors

We have investigated the effects of proton irradiation on the charge collecting properties of planar CdTe detectors. The spatial distribution of the charge collection and of the electric field inside the material has been studied by photocurrent spectroscopy and surface potential analyses. The results indicate that a localized damaged layer is formed under the irradiated electrode due to the presence of a high concentration of electron traps. The induced p
⁺
-type region affects the distribution of the electric field: after irradiation the field is no longer uniform inside the detector but it rapidly decreases to zero towards the damaged layer.