
218 Gallium Nitride (GaN): Physics, Devices, and Technology
where I
0,H
2
,max
is the maximum saturation current for the MIS hydrogen sensors
exposed to the dilute hydrogen ambience at a xed temperature. By combining with
Equations 6.13 through 6.16, the Langmuir isothermal equation above the tempera-
ture of 350 K can be rewritten as follows [20,67]:
1
(/)ln( /)
ln
0,H0,air
O
0,H,max0,air H0,H ,max 0,air
2
II
P
KI IP
e
=×+
β
(6.17)
or
∆φ
=
∆φ
×+
∆φ
β
1
B
O
B,maxH B,max
2
2
P
e
The reaction order β is one for operating temperatures above 348 K [11,12]. For
Pt/β-Ga
2
O
3
(4 nm)/GaN MIS-type hydrogen sensors, the plots of
n
ver-
sus (P
H
2
)
-1/2
in ...