Improvements in CCD Quantum Efficiency in the UV and Near-IR

Improvements in CCD sensitivity in the UV and near-IR by using backside illumination, external backside accumulation, and wavelength conversion phosphors is discussed. Quantum efficiencies of greater than 50% in much of the UV and visible are reported through the use of backside illumination and either UV flood or flash gate backside accumulation. Problems with the environmental stability of backside accumulated CCDs and attempts to control the stability through the use of a biased flash gate is discussed. Significant QE gains in the near-IR through backside illumination without backside accumulation are reported. The use of a high-efficiency wavelength conversion phosphor to increase the UV sensitivity of frontside illuminated CCDs is presented. Results are presented that demonstrate that the QE of a typical polyphase frontside illuminated CCD can be increased from virtually zero to 20% in the UV.