Deterioration of Electrical and Spectroscopic Properties of a Detector Grade Silicon Photodiode Exposed to Short Range Proton, Lithium and Oxygen Ion Irradiation

Abstract

The electrical properties and spectral response of a Hamamatsu S5821 silicon PIN photodiode were investigated in-situ during and after irradiation by 430 keV H+, 2.15 MeV Li2+, 4 MeV O3+ and 6.5 MeV O4+ ion beams focused to a sub-micrometer beam size. Ion species and their respective energies were selected to approximately have the same end range of 5 mum within the depletion region of the unbiased photodiode. Particle irradiation fluences (Phi) of 108 to 1012 cm-2 were selected, such that displacement damage dose (Dd) values within the material had a similar range of 1010 to 10 3 MeV/g for the selected particles. Under these conditions, it has been observed that protons produce the largest increase in device capacitance. At 100 V an increase in the generation current from 2.3 nA/cm2 for a unirradiated sample to 1.7 muA/cm2, 2.4 muA/cm2, and 3 muA/cm2 for samples irradiated by protons, lithium, and oxygen ions, respectively, was determined for a displacement damage dose of 3.9 times 1011 MeV/g. The ion beam-induced charge (IBIC) technique was used to investigate the charge collection efficiency (CCE) of the irradiated photodiodes. The irradiation-induced changes of the CCE for both protons and oxygen were compared with respect to the non-ionizing energy loss (NIEL), which is a good measure of displacement damage introduced into a material by ionizing particles. The measured reduction of the pulse height with increasing displacement damage dose was fitted to a radiation damage function. The calculated equivalent damage factors, K ed, for the proton probe on proton damaged silicon (3.6 plusmn0.4) times 10-15 g/MeV, the proton probe on oxygen damaged silicon (3.90 plusmn0.07) times 10-15 g/MeV , and the oxygen probe on oxygen damaged silicon (3.65 plusmn0.03) times 10-14 g/MeV have been obtained.