CCD development for the Dark Energy Spectroscopic Instrument

We describe research and development efforts directed towards the production of 4 k x 4 k, 15 mu m-pixel, fully depleted CCDs for the Dark Energy Spectroscopic Instrument (DESI). The requirements for DESI include the spectroscopic characterization of large numbers of faint galaxies at high redshift. The identification of the type and the determination of the redshift of the targeted galaxies require the use of thick, fully depleted CCDs with high quantum efficiency at near-infrared wavelengths. We describe our work to improve the CCD performance in terms of quantum efficiency and read noise. We also discuss efforts to reduce the level of image-distortion effects that have been observed on previous CCDs that are due to resistivity striations in the starting silicon and periodic errors in the photomasks used to produce the CCDs.