Electric Field Properties of CdTe Nuclear Detectors

Recently, diode-like In/CdTe/Pt detectors have been realized which look very promising thanks to their enhanced spectroscopic performance. Scope of this work is to investigate the electric field distribution inside these detectors and its temporal evolution by means of the Pockels effect. The implemented set-up allows us to map the electric field and thus to extract the field profiles between the contacts. The analysis shows that the field is mainly confined below the anode. After applying the bias, these detectors are not very stable at room temperature, and they present a pronounced degradation in spectroscopic performance. This degradation is correlated in this work to the evolution of the electric field which has been observed to 'move' towards the anode. We attribute this 'polarization' behavior in CdTe detectors to the concomitance of two factors: the presence of deep levels in the bulk material, and the high hole barrier height of In on CdTe.