Response of 100% internal quantum efficiency silicon photodiodes to 200 eV to 40 keV electrons

Electron irradiation of 100% internal quantum efficiency silicon photodiodes having a thin (60 Å) SiO₂ dead layer results in measured responsivities ranging from 0.056 A/W at an incident electron energy E₀=0.2 keV to 0.24 A/W at E₀=40 keV. A theoretical electron-hole pair creation energy of 3.71 eV, in close agreement with other studies, is derived using a Monte Carlo simulation of electron interactions with the photodiode over an energy range of 1 to 40 keV. Analysis of electron energy lost to processes that do not contribute to electron-hole pair creation shows that the energy lost in the SiO₂ dead layer is dominant for E₀<1.5 keV, whereas the energy removed by backscattered electrons is dominant for E₀>1.5 keV. At E₀=300 eV, the Monte Carlo simulation results show that the electron projected range is significantly less than the dead layer thickness even though the measured response is 0.082 A/W, indicating that electron-hole pairs generated in the oxide dead layer are collected by the junction