High efficiency detection of tritium using silicon avalanche photodiodes

Abstract

This paper describes our recent work in developing low noise silicon avalanche photodiodes (APD) for detection of tritium (/sup 3/H) /spl beta/-particles with high efficiency. In view of the very low energy of /sup 3/H /spl beta/-particles (E/sub max/=18 keV), research was carried out to produce APD structures with a very thin entrance window. This involved using low energy boron implantation into the APD front surface, followed by pulsed excimer laser annealing of the implanted face to form a p/sup +/ contact. The resulting devices had a surface dead layer of about 0.07 to 0.1 /spl mu/m and operated with a low noise threshold (250-300 eV) for 2/spl times/2 mm/sup 2/ size. The /sup 3/H /spl beta/-particle detection efficiency was measured to be approximately 50%. This is about the twice the detection efficiency achieved with standard APDs.