Optoelectronic properties of mercuric iodide crystals for radiation detection

• Published in: Indian journal of pure & applied physics 2004-09, Vol.42 (9), p.653-665
• Main Authors: Sharma, S L, Kumar, G Anil, Acharya, H N
• Format: Article
• Language: English
• ISSN: 0019-5596

Optoelectronic properties of some red mercuric iodide (a-Hgbeta) crystals have been studied for wavelengths 450-700 nm at temperatures 80-300 K. These crystals were grown (a) by solvent evaporation from a-Hgbeta-tetrahydrofurane saturated solution, (b) by hydration of a-Hgbeta-dimethyl sulphoxide-methanol saturated solution and (c) by polymer controlled growth (PCG) in vapour phase. Important aspects of optical generation of the charge carriers have been discussed. The measurements of thermally stimulated currents were also carried out in order to understand the temperature dependence of photocurrents in different wavelength regions. With the computer simulation of the photocurrent versus wavelength spectrum, the room temperature transport properties (the mobility-lifetime products and surface recombination velocities of the two charge carriers) for the crystals of three types have been estimated. For a typical electric field strength of about 2'103 V/cm, the electron drift lengths for the crystals of three types were found to be 1150, 1350 and 6500 mm, respectively, whereas the hole drift lengths were found to be 50, 50 and 150 mm, respectively. As the typical thickness of a-Hgbeta photodetector for any scintillation spectrometer is about 300 mm, under the negative electrode illumination, all the three types of a-Hgbeta crystals present high potential for their use as photodetectors in conjunction with most of the scintillators.