Radiation hardness and lifetime studies of photodiodes for the optical readout of the ATLAS semiconductor tracker

A large sample (96) of epitaxial Si PIN photodiodes has been irradiated by &1MeV neutrons and 24GeV protonswith#uencesupto1015equivalent1MeVneutronscm~2inordertotesttheirsuitabilityforuseintheopticalreadoutofthe ATLASsemiconductortrackerandpixel detector at the CERNLargeHadronCollider. After an initialreductionof30% the responsivity remains constant up to the maximum #uence. The rise and fall times are not signi"cantly a!ectedand remain below 1ns. Although the dark current increases linearly with increasing neutron #uence, its level remainsbelow 100 nAwhich is negligible incomparison tothe operatingphotocurrentwhich is above 100lA. Enhancedageingstudies at 603C have also been carried out and no failure has occurred after an equivalent of 360 years of opera-tion. ( 2001 Elsevier Science B.V. All rights reserved. Keywords: Epitaxial Si PIN photodiodes; Neutron (1MeV) and proton (24 GeV) irradiation; Dark current; Responsivity; Ageing;Lifetime; ATLAS semiconductor tracker; ATLAS pixel detector; LHC