Study On Small Signal Switching Characteristics And Influencing Factors For PbPc Thin Film Transistor

The structure of PbPc TFT is Cu/PbPc/Al/PbPc/Cu.Metal electrodes film were prepared by DC sputtering at a power of 112 W and 128 W in a chamber filled with argon.The organic thin film of the active layer channel material,a small molecule polymer phthalocyanine,was prepared by evaporating at a high temperature of 330? for one hour in an environment of 2.3×10-5 torr.The crystallization state of the surface molecules of PbPc films was analyzed by atomic force microscopy(AFM),and the absorbance of visible light was measured by photometer.In order to make the gate metal Al and the PbPc on both sides form a Schottky contact with rectification,the performance of the PbPc TFT can be optimized by calculating the physical parameters.In this paper,the DC static output characteristics of PbPc TFTs were tested by using a semiconductor test analyzer(Keithley 4200).The test results confirm that the drain-source output current IDS increases as the input voltage VDS is increased.The maximum current density is 3.629 mA/Cm2,and the on/off current ratio is 1.9×105 when the gate-source voltage VGS=OV and VDS=3V.IDS and VDS to meet different function relationships in different VDS range.The Schottky barrier height in the gate region is 0.38 eV and the depletion layer width is 5.43 nm,which are calculated from the capacitance-voltage characteristic at VGS=OV.Under the control of VGS,carriers from the source tunneling through the depletion layer to reach the drain.Calculate carrier mobility and device threshold voltage to characterize the performance of PbPc TFTs.The alternating current are measured and evaluated by the function generator,current amplifier and other related equipments.The results show that the amplitude of AC dynamic output current is consistent with that of DC static output current result.The frequency of the input AC voltage will affect the AC dynamic output characteristics of the PbPc TFT,and the cutoff frequency of the device is 2.3kHz.When the small signal frequency applied to the gate is 2kHz,the turn on time ton=2.5?s,and turn off time toff=3.5?s are obtained.The microsecond switching time indicates that the device has a high response speed.According to the analysis and evaluation of the test results,the PbPc TFT fabricated with the vertical structure of the nano-channel has improved the problem of carrier mobility in the organic semiconducting materials and enhanced conductive carrier transport capability.And the threshold voltage of the PbPc TFT is also lowered.