
55-41Electrochemical Composition Measurement
gets more positive (V
B
>> 0), an inversion layer of n-type Si is created although the substrate is p-type
(in
version regime)
. e el
ectric
be
havior
is gi
ven
by th
e
sm
all-signal
ca
pacitance
of th
e
EI
S
st
ructure
.
e wh
ole
ca
pacitance
(C) ca
n
be de
scribed
as a se
ries
co
nnection
of th
e
me
mbrane
ca
pacitance
(C
M
),
in
sulator
c
apacitance
(C
i
), and space-charge capacitance (C
SC
) of the semiconductor:
1 1 1 1
C C C C
= + +
M i SC
(5
5
.53
)
with
1
C d
A
i
i
=
ε
(55.54)
where
A
i
s
t
he
c
ontact
a
rea
o
f
t
he
g
ate
w
ith
a
n
e
lectrolyte
s
olution
d
i
s
t
he
t
hickness
ε
i
is the permittivity of the gate insulator
C
SC
is, among others, a fu ...