Carrier Transport And Characteristics Analysis Of Organic Thin Film Transistor

In this paper,the prepared transistor choose copper(Cu)as the source and drain,aluminum(Al)as the grid,and organic semiconductor materials of copper phthalocyanine(CuPc)and lead phthalocyanine(PbPc)as the transport layer.Metal electrodes were prepared by magnetron sputtering,and the organic semiconductor layers were prepared by vacuum thermal evaporation.The transistor choose CuPc/Cu/Al/CuPc/Cu five layers stacked vertical structure,to minimize the length of the conducting channel,so as to reduce the driving voltage.Extraction electrode was got with the method of indium granule pressure copper wire.Electrical characteristics were investigated by using KEITHLEY4200 semiconductor characterization system.Experiment data of the transistor rectifier features shows that Al gate with two layer of organic semiconductor CuPc film formed good Schottky contact,and the transport layer CuPc formed good ohm contact with Cu electrode.The diode characteristic shows that the conductive performance of CuPc film is better than CuPc and PbPc hybrid film at same thickness.Static Operating Characteristics shows that the drain-source current(IDS)will decreasing with the increasing of the gate-source voltage(VGS)when drain-source voltage(VDS)at a constant,when gate-source voltage(VGS)at a constant,the drain-source current(IDS)will increasing with the increasing of the drain-source voltage(VDS).Study from the transfer characteristic curve of VGS versus IDS,we can learn that the IDS decreasing quickly when VGS increasing,which reflect that the gate bias voltage has a strong control ability to the drain-source current IDS.The current IDS under the condition of the gate bias voltage is OV is 1000 times of the current IDS when the gate bias voltage is open,can be considered that when the gate open is the same with the base electrode open of the bipolar transistor,the depletion potentials of the gate area in a suspended state,so the Schottky barrier of the depletion layer of the gate region cannot be changed by the source-drain bias voltage VDS,and then the source-gate current IDS is similar to be blocked.The height of Schottky barrier is 0.635eV and 0.617eV which is calculated by capacitance-voltage and current-voltage,respectively.And the carrier concentration obtained by calculation is about 3.231×1015cm-3,the carrier mobility obtained by calculation is 1.1753×10-3cm/Vs.When the gate voltage is zero volts,we can get the working voltage and current expressions of the device is IDS=1.99×10-6exp(qVDS/18.38KT).Experimental results show that the SIT having a short conduction channel structure,help to overcome the disadvantage of the low carrier mobility of the organic semiconductor material,showing the operating characteristics of high-speed,high current density.