Internal Electric-Field-Lines Distribution in CdZnTe Detectors Measured Using X-Ray Mapping

Abstract

The ideal operation of CdZnTe devices entails having a uniformly distributed internal electric field. Such uniformity especially is critical for thick long-drift-length detectors, such as large-volume CPG and 3-D multi-pixel devices. Using a high-spatial resolution X-ray mapping technique, we investigated the distribution of the electric field in real devices. Our measurements demonstrate that in thin detectors, <5 mm, the electric field-lines tend to bend away from the side surfaces (Le., a focusing effect). In thick detectors, 21 cm, with a large aspect ratio (thickness-to-width ratio), we observed two effects: the electric field lines bending away from or towards the side surfaces, which we called, respectively, the focusing field-line distribution and the defocusing field-line distribution. In addition to these large-scale variations, the field-line distributions were locally perturbed by the presence of extended defects and residual strains existing inside the crystals. We present our data clearly demonstrating the non-uniformity of the internal electric field.

Influence of Contacts on Electric Field in an Au/(CdZn)Te/Au Detector: A Simulation

“…The trapping time depends on the concentration of unoccupied trapping sites at deep levels (occupation factor). Studies of the distribution of the electric field in the volume of the devices frequently employed the Pockels electrooptic effect [1]- [3].…”

Detector performance of ammonium-sulfide-passivated CdZnTe and CdMnTe materials

“…In the opposite case, a "focusing" drift-field forming within the device steers the electrons toward the anode. [6] After passivation, the apparent mobility-lifetime product rose in all twelve detectors tested. Fig.…”

“…Comparing the A-center intensities before and after passivation, we note the reduction in the densities of defects. Also, in XPS (X-ray photoelectron spectroscopy) measurements, such changes of surface states, especially for Te, were observed before and after sulfide passivation in both CZT [6] and CMT [1]. Figure 5.…”

Radiation induced control of electric field in Au/CdTe/In structures

“…The effect of time dependent change in charge collection efficiency, known as polarization, has been studied for a long time. [1][2][3][4][5][6] This effect is a result of screening of the electric field by space charge formed due to band bending at contacts with Schottky barriers and takes place even without any radiation. Bale and Szeles 7 have shown, that deformation of the internal electric field profile can be observed at high radiation fluxes even in samples with Ohmic contacts.…”

“…Studies of the distribution of the electric field in the volume of the devices frequently employed the Pockels electro-optic effect. [1][2][3][4] The sample is illuminated with low intensity IR light which has passed through a narrow band-pass 980 nm filter. A pair of 90°o rthogonally orientated polarizing filters are arranged either side of the cryostat, with the transmitted light imaged by an IR-enhanced digital charge coupled device camera.…”