A comprehensive study of short channel effects in organic field-effect transistors

We present a comprehensive study of short channel effects in organic field-effect transistors by measuring the electrical characteristics of devices with fixed channel width and varying channel length. Our studies are conducted on a hole transport organic semiconductor, E,E-2,5-bis-{4′-bis-(4″-methoxy-phenyl)amino-styryl}-3,4-ethylenedioxy-thiophene, that is spin-coated from solution to form bottom contact organic field-effect transistors. Drain–source currents from transistors with a channel length of 50 μm show excellent agreement with the square law equations derived for crystalline Si MOSFETs in both the linear and saturation regimes. As the channel length is incrementally reduced to 1 μm, device characteristics such as saturation regime channel conductance, sub-threshold current and threshold voltage, behave in a manner similar to Si MOSFETs of decreasing channel length. Results of these studies indicate the presence of non-destructive current punch-through and in addition, behavior similar to channel-length modulation and threshold-voltage roll-off, neither of which have previously been reported in OFETs.