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 $\hbox{H} ^{+}$ , 2.15 MeV $\hbox{Li}^{2+}$ , 4$~$MeV $\hbox{O} ^{3+}$ and 6.5 MeV $\hbox{O} ^{4+}$ 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 ${5}~\mu\hbox{m}$ within the depletion region of the unbiased photodiode. Particle irradiation fluences $(\Phi )$ of $10 ^{8}$ to $10 ^{12}\hbox{cm}^{-2}$ were selected, such that displacement damage dose $(D _{d})$ values within the material had a similar range of $10 ^{10}$ to $10 ^{13}\hbox{MeV/g}$ 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 $2.3~\hbox{nA/cm}^{2}$ for a unirradiated sample to $1.7~\mu\hbox{A/cm}^{2}$, $2.4~\mu\hbox{A/cm}^{2}$, and $3~\mu\hbox{A/cm}^{2}$ for samples irradiated by protons, lithium, and oxygen ions, respectively, was determined for a displacement damage dose of $3.9\times 10 ^{11}~\hbox{MeV/g}$. 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 $(3.6 \pm 0.4) \times 10 ^{-15}~\hbox{g/MeV}$, the proton probe on oxygen damaged silicon $(3.90 \pm 0.07) \times 10 ^{-15}~\hbox{g/MeV}$ , and the oxygen probe on oxygen damaged silicon $(3.65 \pm 0.03) \times 10 ^{-14}~\hbox{g/MeV}$ have been obtained.