I've been in the OS research in the last 10 years.

It really depends on the specific couple electrode-semiconductor you use not just on the channel length.

HOwever, there are a number of issues which are pretty common. You can read more in the attached publication. Hope it helps.

Thank you sir, I will contact you if I have any doubts

Thanks Emanuele for the interesting paper.

Very intuitively, the smaller channel, the smaller channel resistance. At some point channel resistance approaches contact resistance, causing the big change in potential drop in your real channel compared to the potential drop from source to drain.