Digital Signal Processing Reference
In-Depth Information
3−pin diode D=G
4−pin diode D=G=BG
10
−5
10
−6
10
−7
10
−8
10
−9
−20
−15
−10
−5
0
5
10
15
20
V
G
[V]
Fig. 2.21
Measured characteristics of a 140
µ
m/5
µ
m original 3-contact transistor diode and a
140
µ
m/5
µ
m 4-contact transistor with the backgate connected to the gate
of organic electronics circuits is the subject of a lot of technological research all over
the world. The focus of this research is to make the technology more performant and
to reduce non-ideal behavior that is present. This non-ideal behavior can be caused
during production, e.g., by a variation of the thickness of a layer,or it can be associated
to the employed materials, e.g., the sensitivity of pentacene to the presence of H
2
Oin
the ambient environment which results in degradation. It is important for the circuit
designer of either digital or analog circuits to be aware of those behaviors so that
they can be overcome at the circuit level. In this section, the non-ideal behavior of
organic pentacene-based thin-film transistors on foil is explored.
2.5.1 Process-Induced Influences
The cross-sectional view of a transistor in the applied organic electronics technology
is shown in Fig.
2.15
. The transistor is built with six different layers of which three
metal layers. The transistor behavior is in all possible ways determined by these
layers: The absolute or relative thickness of the layers, the temperature of the wafer
during a deposition step, the temperature of the material that is deposited during
the deposition, the composition of the environment in the deposition chamber, e.g.,
vacuumor ambient, the speed at which the layers are deposited. The list of parameters
that influence the transistor behavior is endless. A profound examination of the effect
of all those parameters is beyond the scope of thiswork. It is, however, very interesting
and important to have a look at the influence of all these production parameters
together on the behavioral transistor parameters. The current of a transistor biased
in the saturation regime is written in Eq. (
2.4
). In this formula four parameters are
