
46-16 Optical
the theoretical limit of device performance cannot be reached unless the charge collection eciency
substantially exceeds ∼90%. us, in the so x-ray, one requires very high collection eciency over a
re
latively
la
rge
vo
lume
in th
e
vi
cinity
of th
e
ba
ck
su
rface
.
An
y
ba
ckside
fa
brication
te
chniques
wi
ll
pr
obably
re
quire
co
mpromises
to be ma
de,
bu
t
it is po
ssible
to ac
hieve
ve
ry
hi
gh
ex
ternal
QE in th
e
UV
,
as sh
own
in th
e
ac
companying
Fi
gure
46.6 an
d
in th
e
so
x-
ray
re
gion
wh
ere
77
%
QE ha
s
be
en
ac
hieved
at 27
7
eV [1
2]
. Fu
rther
im
provements
ar
e
ne
cessary
to
ac
hieve
go
od
re
sults
in th
e
va
cuum
UV an
d
th
eoretical
li
mits
fo
r
en
ergy
re