To understand which mechanisms dominate the transport charge in Organic Schottky diodes we plot the forward bias log I vs log V of I-V characteristics and thats shows a power law behavior of the current I-Vm+1 with different exponents (m + 1) where (m + 1) varies; after that we distinct the linear regions and fit to calculate the (m + 1) slopes. so somtimes we found 1 linear region and others times 2,3,4,5; my question is : is it good to find more then one conduction mechanism in Organic Schottky diode and which conduction mechanism is better for better transport charge in Organic Schottky diode? any papers about this subject?
Dear Ibrahim,
The metal organic semiconductor junction may behave rectifying or as ohmic contact or may have a mixed behavior according to the barrier height and width between the two materials. If the barrier is wide and high , the junction behaves as Schottky diode and the i-V CHARACTERISTICS is dominated by themionic emission over barriers.
When the barrier is thin the current will be controlled by tunneling.In case of themionic emission the I-V has the form,
I = Is e V/Vt where Is is the reverse saturation current and Vt the temperature equivalent voltage,
In case of tunneling the I-V follows generally a nonlinear empirical relation in the form
I= KV ^m,k and m are curve fitting parameters as hinted by you in your question. Their value depends on the shape of the tunneling barrier and the available charges to cross such barrier..
wish you success
Dear Prof.Dr. Abdelhalim Zekry
Thank you so much for your explanation and your help
Dear Ibrahim,
As it was already mentioned above by Prof. Zekry, there are various processes depending on the energy barrier at the interface or traps in the bulk of the film. Regarding the exponent m I suggest very classical books such as Current Injection in Solids (from Lampert and Mark) or Dielectric Phenomena in Solids (from Kao). Generally speaking the exponent m depends on many parameters including the voltage bias. If we assume interface barrier as a main bottleneck for the charge transport, the barriers are high at low voltages (so the transport will be mainly through the interface states), while at higher voltages will be major thermionic injection or tunneling (the applied electric field is lowering the barrier). On the other hand, the bulk trapping increases exponent m above the space-charge limited current exponent (i.e. V^2), but only up to the trap-fill-limit. There are many publications related to this topic.
Article Charge injection and transport properties of an organic ligh...
Dear, Prof.Dr. Martin Weis
Thank you so much for the explanation and the References.
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