Improvement of the productivity in the growth of CdTe single crystal by THM for the new PET system

Abstract

The effect of the THM growth rate on the CdTe crystalline quality and the detector performance was intensively investigated. The maximum growth rate for the single crystal growth was found to be approximately 15mm/day which was 3 times greater than the conventional one. By optimizing other growth conditions, 90 % of every ingot volume has become a single crystal. Te inclusions in the CdTe single crystal grown at various growth rates were also investigated by IR transmission microscopy. There was no correlation between the behavior of Te inclusions and the growth rate. The detector performance was also independent of the growth rate. Taking advantage of the large volume CdTe single crystals, about 700,000 Schottky detectors with 4 mm × 7.5 mm × 1 mm were fabricated for the research and development of the new PET system using CdTe detectors. The average FWHM for the 662keV line from <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs and its standard deviation were 2.24 % and 0.48 %, respectively. This uniformity was essential for the development of the new PET system. For the further improvement of productivity, the growth technology of a 100mm diameter crystal by THM is in the development and is presented.