Charge transport features of CdTe-based X- and [formula omitted]-ray detectors with Ti and TiO[formula omitted] Schottky contacts

Abstract

The X- and γ-ray detectors, formed as Ti/p-CdTe/Au/Cu and TiOx/p-CdTe/MoOx diode structures with Ti and TiOx Schottky contacts, created by electron-beam evaporation and DC reactive magnetron sputtering of Ti, respectively, have been investigated. The structural, electrical and spectroscopic properties of the Schottky diodes were studied by X-ray diffraction, I–V characteristic and isotope spectrum measurements, respectively. The current transport processes in the Ti/p-CdTe/Au/Cu and TiOx/p-CdTe/MoOx heterostructures at relatively low voltages were well described by the models of the carrier generation–recombination in the space-charge region and space-charge limited current. Comparing the experimental data and calculation results, the energies of generation–recombination centers and hole traps, density of discrete trapping centers were determined, and charge carrier lifetimes. A rapid increase in the reverse current due to the Poole–Frenkel emission was observed and this was attributed to the presence of a thin intermediate insulator layer in the p-CdTe/MoOx interface (near-contact contact). The I–V characteristics of the Schottky diodes have been analyzed using the model of space-charge limited current taking into account the Poole–Frenkel effect. The TiOx/p-CdTe/MoOx detectors were tested using 241Am isotope emission.