Cadmium zinc telluride

Cadmium zinc telluride, (CdZnTe) or CZT, is (as the name indicates) a compound of cadmium, zinc and tellurium or more strictly speaking, an alloy of cadmium telluride and zinc telluride. A direct bandgap semiconductor, it is used in a variety of applications, including radiation detectors, photorefractive gratings, electro-optic modulators, solar cells, and terahertz generation and detection. The band gap varies from approximately 1.4 to 2.2 eV, depending on composition.

Radiation detectors using CZT can operate in direct-conversion (or photoconductive) mode at room temperature, unlike some other materials (particularly germanium) which require liquid nitrogen cooling. Their relative advantages include high sensitivity for x-rays and gamma-rays, due to the high atomic numbers of Cd and Te, and better energy resolution than scintillator detectors. CZT can be formed into different shapes for different radiation-detecting applications, and a variety of electrode geometries, such as coplanar grids, have been developed to provide unipolar (electron-only) operation, thereby improving energy resolution.

The material has a high electro-optic coefficient and transparency in the mid-infrared region, making it a good modulator material for infrared lasers. The same properties make it useful for detection of terahertz waves.

An additional use is as a substrate material for the epitaxial growth of mercury cadmium telluride (HgCdTe), an infrared detector material. Cd_0.96Zn_0.04Te is almost perfectly lattice matched to LWIR HgCdTe (80% Hg, 20% Cd). However, it is difficult to grow large crystals of fixed composition.

Cadmium zinc telluride is highly toxic to humans. It should not be ingested, nor its dust inhaled, and it should not be handled without appropriate gloves. Please refer to materials safety data sheets for details.

References

* Properties of Narrow-Gap Cadmium-Based Compounds Ed. P. Capper (INSPEC, IEE, London, UK, 1994) ISBN 0852968809

External links

* [http://www.evproducts.com/czt.html About CZT]
* [http://www.npi.gov.au/database/substance-info/profiles/17.html National Pollutant Inventory - Cadmium and compounds]