Lateral diffusion in small-pixel CCDs

[Richard Stover]

Posted to CCD-world:
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Roger wrote,

>>I think this raises an interesting question:  if one builds a small
>>pixel CCD, does one have to make it thinner to get comparable MTF.  If
>>so, red response will be sacrificed and fringing will set in at shorter
>>wavelengths and be a stronger effect.  It would seem that eliminating
>>the field free region by deepening the depletion region is preferable
>>both for 8 um and conventional pixel sizes.  As someone involved in a
>>project using high resitivity silicon perhaps you could comment.


Indeed this is exactly my first concern upon hearing about these new
8-um pixel CCDs. Are they going to be thinned more than the standard
CCD with all of the red problems that introduces or are they built on
high-resistivity silicon? If not, then resolution will be significantly
degraded by lateral diffusion. Hopefully the people at Princeton have
taken this into account in arriving at the 8-um size and they realize
that the effective pixel size will be bigger.  High-resistivity silicon
is certainly the best option if Sarnoff has that available.

We were just discussing yesterday the need for some improved lateral
diffusion measurements on Lincoln Labs thinned, high resistivity CCDs
and perhaps we'll have the data ready for presentation at the Kona
conference.

We'll also have data on the thick LBNL high resistivity CCDs. But these
devices have much greater thickness (300um) and a backside bias which
reduces lateral diffusion. So we have some control over the diffusion
in these devices.

Richard


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Richard Stover                           email: richard at ucolick.org
Detector Development Laboratory          http://gardiner.ucolick.org/~ccdev
UCO/Lick Observatory                     Voice: 408-459-2139
University of California                 FAX:   408-459-5244
Santa Cruz, CA 95064  USA                FAX:   408-426-3115 (Alternate)
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