Polarization phenomena in Al/p-CdTe/Pt X-ray detectors

Abstract

Over the last decades, CdTe detectors are widely used for the development of room temperature X-ray and gamma ray spectrometers. Typically, high resolution CdTe detectors are fabricated with blocking contacts (indium and aluminum) ensuring low leakage currents and high electric field for optimum charge collection. As well known, time instability under bias voltage (termed as polarization) is the major drawback of CdTe diode detectors. Polarization phenomena cause a progressive degradation of the spectroscopic performance with time, due to hole trapping and detrapping from deep acceptors levels.In this work, we studied the polarization phenomenon on new Al/p-CdTe/Pt detectors, manufactured by Acrorad (Japan), through electrical and spectroscopic approaches. In particular, we investigated on the time degradation of the spectroscopic response of the detectors at different temperatures, voltages and energies. Current transient measurements were also performed to better understand the properties of the deep acceptor levels and their correlation with the polarization effect.