Schottky-Barrier-Dependence Of Low-Power Consumption And High-Performance OFETs

Organic field-effect transistors?OFETs?have been widely used in active matrix panel display,electroluminescent diode and electronic paper display due to its characteristics of flexible wearable,low-cost,low-temperature preparation and large-area production.However,due to the uncontrollable dopant diffusion in OFETs,ohmic contact cannot be formed between the organic semiconductor and the electrodes.Thus,a high Schottky barrier is formed which greatly affects the performance of OFETs and hinders the realization and development of low-power consumption devices.The first problem to be mined is the extraction of the virtual Schottky barrier height in OFETs because of the electrode surface dipole,metal-semiconductor interface defects,image-force barrier lowering,Fermi-level pinning and so on.The virtual Schottky barrier height is different from the theoretical one.Thus,it is a great challenge for the preparation of high-performance OFETs with ohmic contact.Furthermore,controlling the height of the Schottky barrier to achieve better electrical performance has been a major study.In the past,traditional electrical parameters such as mobility,contact resistance,threshold voltage,and subthreshold swing have been used to evaluate the performance of the device.As a result,the variation of its Schottky barrier has been neglected,and the study of the Schottky barrier controlling in OFETs is rare.Therefore,for OFETs,the way to effectively regulate the Schottky barrier height to optimize the electrical parameters has become a crucial issue.In summary,to realize the large-scale application of OFETs,the reliable extraction method of the Schottky barrier height remains to be studied,and the regulation of the Schottky barrier height with its influence on electrical parameters remains to be discussed.?1?The IDT-BT OFETs with different contact metals?Pt,Au,Cu,Cr?were fabricated to regulate the height of the Schottky barrier.The intrinsic height of the Schottky barrier was extracted and its influence on the electrical parameters of OFETs was studied.The I_on/I_off ratio increases from 10³ to 10⁶ with increasing W_f of contact metals.The mobility increases following the decrease of R_C.The highest mobility of 2.79cm²V^-1s^-1 and lowest R_C of 1.06×10⁴?.cm are observed from Pt-contacted OFETs.After the elimination of the image-force barrier lowering,the intrinsic barrier is extracted from the out-put curves of the device.It is found that the intrinsic value is greatly different from the theoretical value.Furthermore,the smallest intrinsic barrier of?_B,p0=0.123 eV is obtained for Pt-contact OFETs,indicates that nearly ohmic contacts are formed in these devices.Therefore,I_on/I_off,V_th,and SS values of such OFETs are greatly improved.?2?The effects of the Schottky barrier on N2200 OFETs were studied through the indium interlayer at the metal-semiconductor interface.And the effects of different indium thickness on the performance of N2200 thin film transistors were analyzed.It is found that the OFETs with the indium interlayer?10 nm?show the best n-type behavior and electrical performance.The R_c remarkably reduces from 10¹⁰?cm to 10⁸?cm and then increases with the thickness of indium interlayer(T_In).Charge injection could be effectively enhanced by decreasing the height and thickness of energy barriers.The N2200 OFETs with T_Inn of 10 nm exhibits the highest?_SAT(0.324 cm²·V^-1·s^-1)and the lowest SS(0.87 V·dec^-1)values.However,as the T_Inn increases from 10 nm to 20 nm,electron tunneling is suppressed due to the increase of injection distance and thus the OFETs are deteriorated.These results highlight the In interfacial modification behaviors to improve the charge injection and electrical performance of N2200 OFETs.?3?The effects of N2200-In2O3 layers on TFTs were studied.Through the electron doping of In2O3,the optimizing of the device electrical parameters such as the mobility,threshold voltage,and subthreshold swing was analyzed.The electrical parameters of N2200 OFETs,In₂O₃ TFTs and N2200-In₂O₃ TFTs are compared.The N2200-In₂O₃ dual layers structure is found to optimize the threshold voltage of the TFTs.The threshold voltage of the N2200-In₂O₃ TFT is 1.68 V,which satisfies the demand of the low voltage device.At the same time,the bias stability of N2200-In₂O₃ TFT is high.After applying bias voltage?50 V?for 1h,the offset of V_th is only 7.68 V.So the preparation of low voltage and high stability TFT is realized through the N2200-In₂O₃ dual layers.