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Development and fabrication of radiation-stable detectors of gamma-radiation based on CdTe and CdZnTe monocrystals

№47 Division of semiconductor radiation detectors
D.V. Korbutyak

Function:
For control systems of environmental radiation and objects with a high radiation level.
Description of the development:
The pilot experimental batch of radiation-stable (i.e., reliably functioning up to the doses of the order of 1 kGr, or 105 P) semiconductor (CdTe and CdZnTe) detectors of gamma radiation is developed and produced. These detectors can be used in the radiation control devices and exploit under the conditions of high radiation levels (destroyed ChAPP block, territory of alienation, radioactive waste storages, etc.).
Using the proposed technique for contact deposition, it is possible to fabricate high-quality detectors of gamma and X-ray radiation. A smooth transient layer between the metal and the semiconductor formed by a laser alloying of gold into CdTe can not only improve the adhesion as compared to a prototype, but also practically completely eliminate the polarization effect and reduce noises at the metal-semiconductor interface. The most optimal technique to compensate the energy dependence of detectors for applications in the gamma radiation dosimeters is a combination of compensation using physical filters and electronic compensation using multichannel comparators or analog-digital converters.
Basic technical and economic characteristics of the R&D:

• specific resistance  ≥10⁹ Ohm·cm;
• bias voltage  ≤ 1000 V;
• source current  ≤ 0.4 μA;
• the detector energy noise equivalent  ≤ 5 keV;
• energy sensitivity range  0.02 – 3.0 MeV;
• discrete sensitivity  0.02 – 0.05 pulse/S/μR/h;
• the range of equivalent dose of gamma radiation power measurements (137 Cs)  10.0 μR/h – 1.0 R/h;
• range of equivalent gamma radiation dose measurements  100.0 μR – 1.0 R;
• the detectors are radiation-tolerant within the range of gamma-radiation doses of D ≤ 10³ Gr (10⁵ R).

The estimated cost of the developed sensors is about twice as low as the analogous sensors produced by foreign firms.

Evaluation of the project novelty:

The R&D novelty consists in the establishment of relationships between the fundamental CdTe and CdZnTe monocrystal characteristics (mobility and lifetime of nonequilibrium charge carriers, compensation degree, state of impurity-defect subsystem, etc.) and their detector properties. This allowed us to optimize technological regimes used to fabricate radiation-stablet detectors of gamma radiation with preset parameters.
Patent:
Korbutyak D. V., Bobytskyi Ya. V., Budzulyak S. I., Vakhnyak N. D., Demchyna L. A., Ermakov V. M., Krylyuk S. G., Kryuchenko Yu. V. The method of fabrication of a gamma and X-ray radiation detector based on high-resistivity semiconductors CdTe and CdZnTe.  Patent of Ukraine № 46513А of 15.05.2002