ELECTRICAL BEHAVIOR OF LASER-DAMAGED SILICON PHOTODIODES

A measurement of the electrical parameters degradation of Si photodiod es irradiated by laser visible light has been performed. The laser is a Q-switched Nd:YAG, frequency doubled, operated in single pulse mode of 4 ns duration. The applied fluence levels range up to 90 J/cm(2). T wo kinds of irradiation process were applied: either a part of the det ector active area was irradiated in single pulse mode, or a scanning o f the whole detector active area was performed with successive identic al pulses. It has been shown that the fluence necessary to induce sign ificant changes (local decrease of 35%) in responsivity is several tim es the surface melting threshold fluence (0.5 J/cm(2)). Conversely, th e dark current is the most sensitive parameter, increasing by about fo ur times for high irradiation. The in-depth dopant distribution is alt ered by high fluence irradiation in a way that cannot be explained by simple thermal modelling. (C) 1997 Published by Elsevier Science Ltd.