Equivalent Circuit Modeling Of RF Transistors Based On New Ultra-thin Channel Materials

Indium tin oxide and molybdenum disulfide,as new ultra-thin semiconductor materials with atomic layer thickness and high mobility,can reduce short channel effect,boost gate control,and provide the possibility for the realization of high cut-off frequency devices,so they attract the attention of RF field workers.In addition,modeling work can predict device performance,and reduce trial and error cost in experiment,which largely promotes the development of radio frequency fields.However,there is less research on new ultra-thin material RF transistors modeling.Therefore,in order to analyze the DC and RF characteristics of the new material device,and guide the optimization of the device fabrication and the growth of new materials by analyzing the model parameters,the modeling work of indium tin oxide and molybdenum disulfide radio frequency transistors are carried out in this paper,as follows:(1)First,in order to understand the physical properties of channel materials and device architecture,the new material growth and radio frequency device fabrication process were introduced.Then,the DC and RF testing system was introduced,and the calibration and de-embedding process was analyzed to obtain accurate measurement data.Finally,the traditional small-signal circuit model structure and parameter extraction method were introduced to prepare for the new material RF device modeling(2)In this paper,the small signal circuit model of indium tin oxide flexible back gate RF transistor was analyzed.In the first place,the RL series branch was connected in parallel at the output port of the traditional small-signal circuit to describe the channel current magnetic effect,which improved the fitting accuracy of S22 amplitude.Subsequently,the S parameter test data of the three devices with different gate lengths were accurately fitted by the model,which proved that the model has good scalability to the device size.Finally,through the analysis of the model parameters from the three devices with different gate lengths,it was concluded that the RF performance of short channel length indium tin oxide RF devices can be further optimized by reducing the overlap capacitance.(3)In the process of building the small signal circuit of bilayer molybdenum disulfide top-gate radio frequency device,with the help of adding current sources,dispersion resistance Rdb and dispersion capacitance Cdb,the transconductance and output conductance frequency dispersion effect were successfully described.Then Cgb was added to simulate the parasitic path between the top gate and the substrate,which can accurately fit the amplitude of S21 and S12 at high frequencies.According to the analysis result of model parameters,it was necessary to optimize the material growth method to reduce the trap charge and weaken the influence of frequency dispersion effect on the device performance.By analyzing the DC output characteristics of the molybdenum disulfide device,it was found that there was a Kink effect under the high-drain voltage.Then the cause of the kink effect was analyzed and the original Angelov DC model was modified.Finally,the Kink effect was successfully described by the improved DC model,and the accurate fitting of DC characteristics of the device was realized.