Charge Sharing in (CdZn)Te Pixel Detector Characterized by Laser-Induced Transient Currents

Abstract

Performance of the (CdZn)Te pixelated detectors heavily relies on the quality of the underlying material. Modern laser-induced transient current technique addresses this problem as a convenient tool for characterizing the associated charge distribution. In this paper, we investigated the charge sharing phenomenon in (CdZn)Te pixel detector as a function of the charge collected on adjacent pixels. The current transients were generated in the defined 4 mm 2 spots using 660 nm laser illumination. Waveforms measured on the pixel of interest and its surroundings were used to build the maps of the collected charge at different biases. The detailed study of the maps allowed us to distinguish the charge sharing region, the region with a defect, and the finest part in terms of the performance part of the pixelated anode. We observed the principal inhomogeneity complicating the assignment of the illuminated spot to the nearest pixel.Sensors 2020, 20, 85 2 of 14 particular design if wired in a form of a virtual coplanar grid. These detectors are featured by specific electrode configurations that in general provide a particular distribution of electric field inside the sample. According to Shockley-Ramo theorem [13], these field effects induce signal as follows:

Improved electroless platinum contacts on CdZnTe X- and γ-rays detectors

“…Laser induced transient current technique. LI-TCT demonstrated to be a powerful method to measure carrier transport properties 15,[40][41][42] . However, in the papers published up to now, only electron transport properties were determined.…”

Modelling Polarization Effects in a CdZnTe Sensor at Low Bias

“…The counts for 𝑈 < 𝑈 𝑐 are approximated using a straight line, and the point at which maximum counts were achieved is considered to be 𝑈 𝑐 ≈ 265 V. This procedure was repeated for each pixel, and the distribution of 𝑈 𝑐 is shown in Figure 8. The decrease in measured counts at low bias is not mainly caused by carrier trapping but by the ballistic deficit of low energy X-ray photons, which do not cross the threshold level, frequent pileups, and charge sharing between pixels [19], which is accentuated at the low electric field near the pixelated anode. In Figure 9, we show the current waveforms calculated using Equation ( 2) with the electric field obtained from the numerical simulation with the X-ray photon absorbed close to the cathode, and the use of the weighting field is plotted in Figure 6.…”

“…This procedure was repeated for each pixel, and the distribution of is shown in Figure 8 . The decrease in measured counts at low bias is not mainly caused by carrier trapping but by the ballistic deficit of low energy X-ray photons, which do not cross the threshold level, frequent pileups, and charge sharing between pixels [ 19 ], which is accentuated at the low electric field near the pixelated anode.…”

“…Simulations of semiconductor radiation detectors were studied in [ 14 , 15 , 16 , 17 , 18 ] to obtain charge transport properties. Charge transport in pixelated detectors was studied in [ 19 , 20 , 21 ], where the effects of charge sharing and material quality on detector performance were investigated.…”

Charge-Sharing Detection Method Using Semiconductor Detectors with Different Electron and Hole Mobilities

“…Incident photons on detectors equipped with multiple electrodes yield signals of opposing polarities at adjacent electrodes. (13)(14)(15) This phenomenon is associated with situations where the incident location of the photon lies near the electrode boundary. The mobilities of the electrons and holes in the detector differ significantly.…”