Design and manufacture of CdZnTe semiconductor detector for gamma ray detection

Abstract

In this paper, the process of crystal selection, samples preparation and method of shottkey and ohmic contacts creation for CdZnTe or CZT detector, to be used as a portable device operating at room temperature, have been reported. First, the ratio of CZT element and crystal dimensions was determined via MCNP4C code and its effect on the electrical and detection behavior was investigated. After the crystal preparation, its surface was activated by chemical method. On one side, Au with a thickness of 100nm was coated as a schottkey contact and on the other side, in was coated as an ohmic contact with physical vapor deposition. The electrical characters of the sensor such as current-voltage, current-capacitance and current-temperature were measured. The sensor was connected to a pre-amp, pulse shaping, amplifier and MCA. The detector was tested by point sources of Cs-137 and Th-232, and was calibrated by standard uranium samples. The results showed that the FWHM of 662 keV is 3.8 keV and the error for the enrichment determination was less than 3%.

Keywords

• czt crystal
• schottkey contact
• ohmic contact