Electronic devices based on organic semiconductors, mainly conjugated
polymers, have recently been reported. In this paper characterization
and improvements of three devices will be presented, namely, Metal Oxi
de Semiconductor Field Effect Transistors (MOSFET), Schottky barrier d
iodes and Schottky gated Field Effect Transistors (MESFET). The MOSFET
devices work through the modulation of an accumulation layer at the s
emiconductor (polymer)-insulator interface. A model for organic MOSFET
is proposed by changing the classical equations according to this par
ticular operating mode. It is shown that, the characteristics of these
organic devices can be improved by controlling the doping in certain
level and decreasing the thickness of the semiconducting (polymer) lay
er. The mobility also increases with the gate bias in contrast to inor
ganic semiconductor. A planar Schottky barrier diode is successfully f
abricated and reported, using poly (3-alkylthiophene) as an active sem
iconductor and aluminium and gold electrodes are used as Schottky and
ohmic contacts. The electrical characteristics of the poly (3-alkylthi
ophene)/metal interfaces have been studied. Electrical characterizatio
n reveals diode behaviour with a rectification ratios larger than 10(4
) at sufficiently high voltage. The ideality factor (n) is as low 1.2.
Possible transport mechanisms are discussed. In this paper also fabri
cation and characterization of Schottky gated planar field effect tran
sistors using poly(3-alkylthiophene) as an active material am reported
. Aluminium is used for the rectifying contact and two gold electrodes
are used as source and drain. From the MESFET characteristic the chan
nel carrier mobility is evaluated to be 10(-5) cm2/Vs, which is one or
der of magnitude larger than than mobility found from an MOS transisto
r using the same polymer.