Accumulated-carrier screening effect based investigation for the pixellated CdZnTe radiation detector

Based on the pixellated CdZnTe detector, the radiation imaging experiment for the Rh target X-ray source is accomplished. The experimental results indicate that the response signals of the anode pixels, which distribute over the center irradiated area, are completely shut-off when the tube voltage is 45 kV and the tube current increases to 20 µA. Moreover, the non-response pixel area expands with the increase of the tube current, and the total event count of the CdZnTe detector reduces obviously. Furthermore, the inner electric potential and electric field distributions of the pixellatedCdZnTe detector are simulated based on the Poisson equation. The simulation results reveal that the accumulation of the hole carriers, which resulted from the extremely low drift ability of the hole carrier, leads to a relatively high space-charge-density area in the CdZnTe bulk when the irradiated photon flux increases to 5×10⁵ mm⁻² · s⁻¹. And thus, the induced signal screen effect of the anode pixels in the center irradiated area is mainly attributed to the distorted electric field which makes electron carriers drifting toward the high potential area in the CdZnTe crystal instead of the pixelanodes.