  In this paper, two dimensional modulation of the potential in sexithiophene (T6) / N,N-bis(n-octyl)-dicyanoperylenediimide (PDI-8CN2) heterojunction field effect transistors due to the specific microstructure at the interface is used to explain the negative transconductance effect (NTC) experienced in sexithiophene (T6) / N,N-bis(n-octyl)-dicyanoperylenediimide (PDI-8CN2) heterojunction field effect transistors. The NTC effect has been experienced in tunnel devices, such as the tunnel diode, the resonant tunneling field effect transistors (RT-FETs), resonant tunneling double barrier devices. In grid-gate modulation-doped field effect transistors, instead, a periodic potential barriers in the direction of the transport of charges was used to explain the negative transconductance (NDR). Since in T6 / PDI-8CN2 heterojunction field effect transistors the NTC effect is irrespective of the order of the semiconductor layer and since the modulation of the transport properties is deeply influenced by the island dimension of the semiconductor layer, we argue that the origin of the NTC effect resides in the achievement of a specific microstructure of the heterostructure in the charge transport plane. 
Microstructured tunable two dimensional potential modulation in organic   heterostructure field effect transistors