Response of 100% internal carrier collection efficiency silicon photodiodes to low-energy ions

We measure the response of silicon photodiodes to irradiation by H ⁺, He⁺, C⁺, N⁺, O⁺, Ne⁺, and Ar⁺ ions with energies up to 60 keV. The unique properties of these photodiodes, including an ultrathin SiO₂ dead layer and 100% internal carrier collection efficiency, allow direct measurement of the total energy lost to nuclear (nonionizing) and electronic (ionizing) energy loss processes, which are important for quantifying effects such as damage and charge deposition. When plotted as a function of E/mZ^1/2, where E, m, and Z are the incident ion energy, mass, and atomic number, respectively, the responsivity is found to follow a single curve that represents all ion species and energies used in this study. This enables rapid, accurate estimation of damage and charge deposition by an ion as a function of penetration depth in silicon. A comparison of the measurements with the stopping and range of ions in matter (SRIM) Monte Carlo simulation code shows that SRIM significantly overestimates the fraction of the incident energy lost to electronic stopping processes for E/mZ^1/2<2 keV/amu