Improving the performance of CdZnTe detectors using infrared stimulation

The influence of monochromatic optical stimulation with wavelengths from 400 nm to 1100 on characteristics of the CdZnTe quasi-hemispherical detectors was studied. It was found that illumination with infrared (IR) light of wavelengths (870-900 nm) close to the absorption edge of the CdZnTe significantly improves the detectors performance at room temperature. Improvement can be achieved with low-intensity IR illumination of about 1-10 μW. The higher intensity illumination leads to degradation of the detector spectrometric characteristics. Infrared radiation penetrates into the detector sensitive volume, change the balance equilibrium between free and trapped carriers, leading to improve charge collection. For practical use as an IR source is suggested to use IR LED. We have tested various LED with a wavelength of the emitted light from 770 to 1020 nm. The degree of improvement is individual for different detectors, depending on the source material characteristics used for detector fabrication and its dimensions. For example a detector of sizes 5×5×2.5 mm³ with an initial energy resolution (FWHM) 7.0 keV at 662 keV was improved with IR LED illumination up to 4.8 keV. IR stimulation improves spectrometric characteristic in a wide range of energies starting from 59.6 keV without loss of detection efficiency and in a wide temperature range from -30 °C to +70 °C. The use of IR illumination with a properly chosen wavelength not only improves the performance of detectors at low temperatures, but also stabilizes them in time.