cryogenic CCD operation

[Barry E. Burke]

Posted to CCD-world:
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Tim,

Conventional buried-channel CCDs cannot be operated below about 70 K.  At
these temperatures the electrons (I'm assuming an n-channel device) begin
to "freeze out" on the donors in the buried channel, that is, the thermal
energy is barely sufficient to ionize the donors.  Thus, the donors begin
behaving as traps, and the CTE deteriorates.  All three useable donor
species in silicon (P, As, Sb) have about the same ionization energy
(roughly 10-13 meV).  A p-buried channel device using boron would be even
worse (ionization energy=45 meV).  Around 10 years ago a Japanese paper
appeared that demonstrated operation down to 50-60 K using a lightly doped
n-buried channel, but I can't find the reference.

Surface-channel CCDs will work down to 30 K or lower, but of course the CTE
will not be great.  There is little written on this subject, but it was
studied many years ago in the IR community.  Perhaps someone out there from
Hughes or Rockwell can provide some information.

Barry Burke


>Posted to CCD-world:
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>I have heard that CCDs cannot be operated at extremely cold
>temperatures (I'm looking at an application which would operate
>around 30K). Does anyone have any information on this?
>What is the failure mechanism? Has anyone tried it? What is the
>cutoff temperature?  Is there any published research on this topic?
>
>
>Thanks for your help,
>
>Tim
>
>
>________________________________________________________________________
>
> Tim Hardy
> National Research Council Canada          E-mail: Tim.Hardy at hia.nrc.ca
> Herzberg Institute of Astrophysics        Phone:  (250) 363-0015
> 5071 W. Saanich Road                      FAX:    (250) 363-0045
> Victoria, B.C.   V8X 4M6
>
>                    http://www.hia.nrc.ca/STAFF/timh
>________________________________________________________________________
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Barry E. Burke
Senior Staff Member
M.I.T Lincoln Laboratory, M.S. LI-127
244 Wood Street
Lexington, MA 02420-9108          -> Please note new postal zip code!
E-mail: bburke at LL.MIT.EDU
Phone: (781) 981-0680; FAX: (781) 981-5957    -> Please note new area code!
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