Control of device parameters by active layer thickness in organic field-effect transistors

We investigate the effect of the parasitic access resistance on device parameters, particularly the threshold voltage $(VT)$ and the contact resistance $(RC)$⁠, of staggered organic field-effect transistors by varying the active layer thickness $(ds)$⁠. At low gate voltages, $RC$ decreases as $ds$ increases due to the free carrier density increasing in the semiconductor film. At high gate voltages, $RC$ increases as $ds$ increases due to increasing access resistance. These factors degrade the device parameters with increasing $ds$⁠. The contribution of the change in $ds$ on the $VT$ shift is assessed by subtracting the contact effect from the apparent $VT$⁠.