The performance of CdZnTe (CZT) detectors is limited not only by conventional carrier-trapping to point defects but also by trapping at macroscopic Te secondary-phase defects, such as Te inclusions and Te precipitates. The aim of this research is to remove these secondary-phase defects via thermomigration, and to obtain high resistivity of the material by creating Te antisites through annealing in a high Te overpressure. We annealed Te-rich CZT samples in the temperature range between 500 and 700 °C under Te overpressure with a temperature gradient of 50-60 °C/cm. We investigated the effects of annealing under these conditions by IR transmission microscopy, current-voltage measurements, photoluminescence, and white-beam X-ray diffraction topography (WBXDT) measurements comparing the findings with those from isothermally annealed CZT samples under Cd overpressure. We proved experimentally that Te inclusions present in Te-rich CZT melts contain void fractions. We attributed the complex defect of Te antisites with Cd vacancies in our annealing experiment as the deep level defect that pins the Fermi near the middle of the bandgap, rather than the Te antisite.
Bibliographical noteFunding Information:
This work was supported by the U.S. Department of Energy , Office of Nonproliferation Research and Development, NA-22 and the Defense Threat Reduction Agency .
- A1. Defects
- A1. X-ray topography
- A2. Bridgman technique
- B1. Cadmium compounds
- B2. Semiconducting II-VI materials
ASJC Scopus subject areas
- Condensed Matter Physics
- Inorganic Chemistry
- Materials Chemistry