HIGH-EFFICIENCY DETECTION OF TRITIUM USING SILICON AVALANCHE PHOTODIODES

This paper describes our recent work in developing low noise silicon a valanche photodiodes (APD) for detection of tritium (H-3) beta-particl es with high efficiency. In view of the very low energy of H-3 beta-pa rticles (E-max=18 keV), research was carried out to produce APD struct ures with a very thin entrance window. This involved using low energy boron implantation into the APD front surface, followed by pulsed exci mer laser annealing of the implanted face to form a p(+) contact. The resulting devices had surface dead layer of about 0.07 to 0.1 mu m and operated with low noise threshold (250-300 eV) for 2x2 mm(2) size. Th e H-3 beta-particle detection efficiency was measured to be approximat ely 50%. This is about the twice the detection efficiency achieved wit h standard APDs.