The detector material used in this experimments is Ultra-High Purity p-type Si crystal. The material was single-crystalized through floating zone process from poly-crystal grown by thermal decomposition of highly refined mono-silane gas which had been purified by molecular sieves of specially prepared Zeolite powder.
The resisitivity at room temperature is normally above 30 kΩ.cm, and the value of the highest grade ones exceeds 100kΩ.cm which corresponds to the Boron concentration of 1.5×l011 B/cm3.
The potentiality of this material for detector use was investigated through Surface Barrier Detector fabrication. Detectors of above 4 mm thick and of excellent characteristics both at room temperature and at liq. N2 temperature could readily be fabricated. Owing to tie extremely high resisitivity, detectors can be made either partially depleted or totally depleted simply by properly selecting the wafer resisitivity and the thickness.
In detector fabrication, the proper surface chemical treatment is very important, and seriously affects the leakage current and breakdown characteristics.
Ultra-High Purity Si is promising as new detector material and has good potentiality to replace Si(Li) as followings:
1) simple and easy detector fabrication,
2) potentiality of thick detector fabrication (∼1cm),
3) no precipitation problem of Li ions, and
4) feasibility of thick ⊿E detector with thin entrance window on both faces.