CCD research and development at Lawrence Berkeley National Laboratory

Abstract

We describe work at Lawrence Berkeley National Laboratory (LBNL) to develop enhanced performance, fully depleted, back-illuminated charge-coupled devices for astronomy and astrophysics. The CCDs are fabricated on high-resistivity substrates and are typically 200–300 μm thick for improved near-infrared response. The primary research and development areas include methods to reduce read noise, increase quantum efficiency and readout speed, and the development of fabrication methods for the efficient production of CCDs for large focal planes. In terms of noise reduction, we will describe technology developments with our industrial partner Teledyne DALSA Semiconductor to develop a buried-contact technology for reduced floating-diffusion capacitance, as well as efforts to develop ”skipper” CCDs with sub-electron noise utilizing non-destructive readout amplifiers allowing for multiple sampling of the charge packets. Improvements in quantum efficiency in the near-infrared utilizing ultra-high resistivity substrates that allow full depletion of 500 μm and thicker substrates will be described, as well as studies to improve the blue and UV sensitivity by investigating the limits on the thickness of the back-side ohmic contact layer used in the LBNL technology. Improvements in readout speed by increasing the number of readout ports will be described, including work on high frame-rate CCDs for x-ray synchrotrons with as many as 192 amplifiers per CCD. Finally, we will describe improvements in fabrication methods, developed in the course of producing over 100 science-grade 2k × 4k CCDs for the Dark Energy Survey Camera.