Characterisation of Redlen HF-CdZnTe at > 106 ph s-1 mm-2 using HEXITECMHz

Abstract

In this paper, results are presented from the characterisation of Redlen Technologies high-flux-capable Cadmium Zinc Telluride (HF-CZT) hybridised to the HEXITECMHz  ASIC, a novel 1 MHz continuous X-ray imaging system. A 2 mm thick HF-CZT HEXITECMHz detector was characterised on the B16 Test Beamline at the Diamond Light Source and displayed an average FWHM of 850 eV for monochromatic X-rays of energy 20 keV. Measurements revealed a shift in the baseline of irradiated pixels that results in a movement of the entire spectrum to higher ADU values. Datasets taken to analyse the effect's dynamics showed it to be highly localised and flux-dependent, with the excess leakage current generated equivalent to per-pixel shifts of ∼ 543 pA (8.68 nA mm-2) at a flux of 1.26×107 ph s-1 mm-2. Comparison to results from a p-type Si HEXITECMHz device indicate this `excess leakage-current' effect is unique to HF-CZT and it is hypothesised that it originates from trapping at the electrode-CZT interface and a temporary modification of the potential barrier between the CZT and metal electrode.