Study Of Large Signal Model Of AlGaN/GaN High Electron Mobility Transistors

Since the 1950s,silicon has always been the most important material in the semiconductor field,with the continuous de-velopment of microelectronics technology.the performance of silicon-based power devices is close to its theoretical limit,the speed of improvement has slowed down.In order to meet the requirements of semiconductor devices operating at higher frequencies and higher power,third-generation semiconductor materials represented by GaN are on the industrial stage,since gallium nitride(GaN)materials have many advantages,they have been recognized as the most promising materials for next-generation power devices.As a representative of GaN-based devices,AlGaN/GaN HEMTs have also been commercialized.GaN-based devices have been used in many fields,especially microwave,high power field.With the advent of the 5G era,GaN-based devices may attract more attention.The application of GaN base is inseparable from circuit design,the device model plays an important role in circuit design.In response to the above problems,we have done a series of work on modeling AlGaN/GaN HEMTs,mainly includes:1.Physical model of current-voltage(?-?)characteristics of AlGaN/GaN HEMTs.The physical model of AlGaN/GaN HEMT devices is of important basis for building AlGaN/GaN HEMT device models,the physical model of AlGaN/GaN HEMTs includes ?-? characteristics(device output characteristics)and capacitance-voltage(C-V)characteristics.Polarization is an important feature of GaN material systems,while the AlGaN/GaN HEMTs are operated,the polarization charge at the heterojunction interface distributed unevenly,and the channel electrons are affected by the polarization coulomb field(PCF)scattering.PCF scattering is an important scattering mechanism for carriers of AlGaN/GaN HEMTs,which has an important influence on the characteristics of AlGaN/GaN HEMTs.It's the first time that we introduced the PCF scattering effect into the physical model of ?-?characteristics of AlGaN/GaN HEMTs:combining with AlGaN/GaN HEMTs we made and using the polarization coulomb field scattering theory,the change of low field carrier mobility(?)and the parasitic series resistance(Rs)of the gate source and the parasitic series resistance(RD)of the gate drain under different gate-source bias voltages VGs are analyzed and calculated.The I-V output characteristic curve of the AlGaN/GaN HEMTs obtained by the simulation is in good agreement with the I-V output characteristic curve obtained by test,therefore,the important role of polarization coulomb field scattering effect in the physical model of I-V characteristics of AlGaN/GaN HEMTs is clarified,a physical model of I-V characteristics of AlGaN/GaN HEMTs includes polarization coulomb field scattering effects was established.2.Extraction of small signal equivalent circuit parameters of AlGaN/GaN HEMTs.We fabricated the sub-micron gate length AlGaN/GaN HEMTs,and a 15-element equivalent circuit model was used to extract small signal parameters.The values of the individual components were extracted according to the measured small-signal S-parameters.In this paper,the value of the gate-source and gate-drain resistance extracted by the thermal field method varies with the bias point.It further shows that the polarization coulomb field scattering effect has an important influence on the characteristics of AlGaN/GaN HEMTs.3.Nonlinear equivalent circuit model of AlGaN/GaN HEMTs.In order to combine with EDA(electronic design automation)software better,the Curtice cubic model is used to fit the I-V output curve of the device.According to the extracted device parameters and the large-signal equivalent circuit structure,we establish the large-signal SDD model of AlGaN/GaN HEMTs.The built model is embedded into the DC and S-parameter simulation circuit,the I-V output characteristic curve and the small-signal S-parameter of the model are obtained by simulation,which is consistent with the I-V output characteristic curve and the small-signal S-parameter measured by the actual device,which proves that we establish the correct model.4.Linearity study of GaN HEMT devices.Using Cree's CGH60008D,CGH60015D,CGH60030D GaN HEMT device large-signal model,through ADS harmonic simulation,the power gain,efficiency,1dB compression point and other parameters of three different gate width devices at different frequencies are obtained.Discussing the effect of frequency and gate width on device linearity.