Current saturation effect for pentacene-based static induction transistor under negative drain-source and gate voltages

Usually, the drain-source current (I_DS) increases with positive drain-source voltage (V_DS) for pentacene-based organic static induction transistor (OSIT) ITO(Source)/Pentacene/Al(Gate)/Pentacene/Au(Drain) and it shows an inherent rectifying property under negative gate voltages (V_G), i.e. the slope of I_DS vs. V_DS curve increases with V_DS but without any current saturation effect. In this paper, we investigated the electrical characteristics of pentacene-based OSIT ITO/Pentacene(80 nm)/Al(15 nm)/Pentacene(80 nm)/Au under negative V_DS and V_G, and found that I_DS changed from rectifying property to saturation effect when the magnitude of negative V_DS was increased from 0 V to -6 V under negative V_G, and the turn-on voltage (V_ON) moved to larger negative voltages when the magnitude of negative V_G increased and the movement step of V_ON gets smaller after keeping the device for a long time, and the possible mechanisms for such a kind of current modulation were discussed.