Electric field distribution and charge transport properties in diode-like CdTe X-ray detectors

The physical behavior of electrode contacts and their technology is an active field of interest in room-temperature semiconductor detectors, where low currents at high electric fields are extremely desirable. Recently, CdTe detectors having a diode-like In/CdTe/Pt structure have been realized which are able to sustain very high applied reverse voltages while limiting the dark current at low values; moreover, in terms of energy resolution, they show excellent characteristics respect to conventional devices based on symmetric contacts. In this work, we investigate the electric field distribution inside these diode-like detectors by using the linear electro-optic effect (Pockels effect). We also discuss their local charge collection properties, accessed by performing IR pulsed laser experiments. These techniques, in conjunction with the analysis of current–voltage curves, allow us to consistently evidence the strong hole-blocking nature of the In contact. In order to analyze the different characteristics of the In and Pt contacts and how these contacts affect the detector charge collection properties, we compare the results with those obtained from a conventional Pt/CdTe/Pt structure.