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

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 Li(2+), 4 MeV O(3+) and 6.5 MeV O(4+) 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 mu m within the depletion region of the unbiased photodiode. Particle irradiation fluences (Phi) of 10(8) to 10(12) cm(-2) were selected, such that displacement damage dose (D(d)) values within the material had a similar range of 10(10) to 10(13) 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/cm(2) for a unirradiated sample to 1.7 mu A/cm(2), 2.4 mu A/cm(2), and 3 mu A/cm(2) for samples irradiated by protons, lithium, and oxygen ions, respectively, was determined for a displacement damage dose of 3.9 x 10(11) 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 +/- 0.4) x 10-(15) g/MeV, the proton probe on oxygen damaged silicon (3.90 +/- 0.07) x 10-(15) g/MeV, and the oxygen probe on oxygen damaged silicon (3.65 +/- 0.03) x 10(-14) g/MeV have been obtained.