X-ray detector with increased detective quantum efficiency

摘要

An x-ray detector having an increased DQE (detective quantum efficiency) is provided. The x-ray detector includes a scintillator for converting incident x-ray photons into optical photons, and an epitaxial p-i-n photodiode for converting these optical photons into an electric signal. The epitaxial photodiode includes a low resistivity N⁺ type silicon substrate; a high-resistivity, N-type epitaxial layer that forms the intrinsic region of the photodiode; and a light-receiving P⁺ type layer. The resistivity of the N⁺ layer is sufficiently low, so that the diffusion lengths of the charge carriers that are formed in the N⁺ layer by direct conversion of x-rays are small enough to allow these charge carriers to recombine before reaching the pn junction. The resistivity of the epitaxial N-layer is high enough so that the collection efficiency of the output signal resulting from the electron-hole pairs created through absorption of the optical photons in the depletion region is not impaired.