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In this paper we present the development of quasi-hemispherical gamma-ray detectors based on CdZnTe. Among the possible single-polarity electrode configurations, such as coplanar, pixelated, or virtual Frisch-grid geometries, quasi-hemispherical detectors are the most cost-effective alternative with comparable raw energy resolution in the high and low energy range. The optimal configuration of the sensor in terms of dimension of the crystals and electrode specifications has been first determined by simulations, and successively validated with experimental measures. Spectra from different sources have been acquired to evaluate the detectors performances. Three types of detectors with different CZT volumes have been fabricated, namely 10 × 10 × 5 mm 3 , 15 × 15 × 10 mm 3 and 20 × 20 × 10 mm 3 . In the case of 10 × 10 × 5 mm 3 crystals, the optimum pixel size determined by our simulation tool was confirmed by experiments: the best spectroscopic resolution of 1.3% at 662 keV has been found for a 750 μm diameter pixel detector. The best energy resolution values obtained for the 15 × 15 × 10 mm 3 and 20 × 20 × 10 mm 3 detectors were respectively 1.7% and 2.7% at 662 keV., (© 2023. The Author(s).)

Platinum is a promising candidate for the realization of blocking electrical contacts on cadmium-zinc-telluride (CdZnTe or CZT) radiation detectors. However, the poor mechanical adhesion of this metal often shortens the lifetime of the final device. In this work, a simple and effective procedure to obtain robust platinum contacts by electroless deposition is presented. Microscopical analysis revealed the final thickness and composition of the contact layer and its adhesion to the bulk crystal. The blocking nature of the Pt-CdZnTe junction, essential to obtain low noise devices, was confirmed by current-voltage measurements. The planar Pt-CdZnTe-Pt detectors showed good room temperature spectroscopic performance with energy resolution of 4% (2.4 keV) and 3% (3.7 keV) FWHM at 59.5 and 122.1 keV, respectively. Finally, we showed, for the first time, that platinum contacts allow the estimation of the carrier lifetime and mobility of both holes and electrons by using current transient measurements. This demonstrated the optimal hole extraction capability of such contacts.