Silicon sensors with integrated UV filters for fast scintillation detectors and solar-blind imaging systems*

We report on the development of device-integrated metal dielectric filters to enable solid-state silicon sensors to operate at ultraviolet wavlengths with solar or visible blindness. One application of these devices is for scintillation based platforms where deep-diffused silicon avalanche photodiodes have been designed to detect the fast emission component of BaF₂ scintillators centered around 220 nm. Traditional silicon photodetectors have poor sensitivity at wavelengths in this range due the short absorption depth of deep UV photons. This is overcome by the use of molecular beam epitaxy to create 2D superlattice-doped surfaces that restore high internal UV quantum efficiency. Integrated deep UV bandpass filters are deposited directly onto the silicon surface to maintain high in-band sensitivity to the fast BaF₂ emission component, while simultaneously rejecting a larger and slower component centered at 330 nm. This concept can be extended to imaging sensors like CCDs for astrophysics applications where visible or solar blindness is often desired. The performance of these devices and the design and fabrication challenges associated with this development will be discussed.