revisit papers by Prof. Iniguez' group. They are discussion mobility measurements in the oFETs.

Generally, the mobility is calculated by measurement of the saturation current (equations can be found on Google and in research publications). As you write, in short channels, the effects of other physical quantities become important. If you are worried about the injection "resistance", you can eliminate that by measuring the saturation current with different channel lengths. If you are worried about other short channel effects, the mobility in OFETs is generally too low to be hugely impacted by velocity saturation - especially for 900nm channels. Scattering effects are important, and it is crucial to test with the right insulator interface, but they can be problematic even for long channel devices.

@ Wladek Grabinski

Thank you very much sir for your great information

@ Raoul Schroder

Thank you very much sir for your analysis, here I am worrying about drift velocity.

can i get about that?

You could try to estimate the carrier concentration from the threshold voltage of your field effect measurements and then calculate the field effect mobility. We have done this for InAs nanowires (c.f. doi:10.1063/1.3631026).

This method has certain drawbacks but it can deliver a first estimate.

Article Effect of Si-doping on InAs nanowire transport and morphology

The effective mobility also can be extracted via C-V split measurement, remember that the effective mobility is larger tht field effect mobility (µFE =(L gm) / (WCox Vd ) ), it can be found in lots of sources, but the capacitance is very important here.

Please, see e.g.

Yong Xu, Mohamed Benwadih, Romain Gwoziecki, Romain Coppard, Takeo Minari et al., "Carrier mobility in organic field-effect transistors", J. Appl. Phys. 110, 104513 (2011);

And, please, keep in mind, that we try to apply a formalism developed for MOS devices (solid state devices), whereas in OFETs the transport mechanism is different.

@ Arash Dehzangi

Thank you very much for your great information

@Daniel Tomaszewski

Thank you ,I am going through that article, If I have any doubt, will contact you

@ Daniel Tomaszewski

ya, I want to know much about OFET Transport mechanism, If you know much about please..

There are many works considering the topic. E.g. I've found a PhD thesis, which may be helpful for you.: www.ruf.rice.edu/~natelson/theses/behranghamadani_thesis.pdf‎

or another work http://inside.mines.edu/~zhiwu/research/papers/G02_charge_transfer.pdf

An appropriate query in Google will indicate a number of papers.

Also http://www.jacobs-university.de/phd/files/1273582720.pdf

In PhD dissertations there are many references.

@ Daniel Tomaszewski

Thank you sir

Our group has been working on organic field effect transistors for years and of course, mobility. Please feel free to check out our homepage and our papers, were mobility measurements are described.

http://www.pnm.ethz.ch/research/Organic_Electronics

I think mobility in organic devices, could be extracted versus time of fiy(TOF) and addmittance spectroscopy(AS) methods. For OFET you should add additional bias.

@ Thomas Mathis, Thank you , I have gone through your link and got good information,Really it is very useful for me..Thank you once again