Studies Of AlGaN/GaN HEMT Device Modeling Based On ASM-HEMT Compact Model

AlGaN/GaN High Electron Mobility Transistor(HEMT)and its models have been the focus of academic research and industrial applications in the past decades.The primary reason is that it has the characteristics of high charge density,high electron mobility,high breakdown voltage and so on.Secondly,due to the existence of polarization effects(piezoelectric polarization and spontaneous polarization)in AlGaN/GaN heterojunction,Two-dimensional Electron Gas(2DEG)with above-mentioned characteristics can be formed at the interface of AlGaN/GaN heterojunction even if the AlGaN layer is not deliberately doped.In order to apply AlGaN/GaN HEMT devices with these excellent characteristics to the industrial applications as soon as possible,it is necessary to simulate the circuits accurately and quickly based on AlGaN/GaN HEMT devices,and the compact model used for AlGaN/GaN HEMT devices determines the accuracy and convergence of the simulation.ASM-HEMT model is a physical based compact model certified by Compact Model Council(CMC),and the drain current expression and the each port intrinsic charge expression are derived based on the relationship between the surface potential and 2DEG surface density.Then,more accurate expressions of drain current and intrinsic charge are derived by considering various real physical effects of the device.In this paper,ASM-HEMT model parameters extraction,influence mechanisms of channel electron mobility under gate,device modeling and GaN-based class A power amplifier performance simulation have been studied deeply based on ASM-HEMT compact model.The specific contents are as follows:1.ASM-HEMT model parameters extraction for AlGaN/GaN HEMT device.Aiming at the small-size AlGaN/GaN HEMT devices fabricated by our research group,it is the pioneer in the industry to use the BSIMProPlus EDA software and the ASM-HEMT compact model to complete model parameters extraction.the fine consistency between measurement datas and simulation datas proving that the extracted model parameters are reasonable.2.Research on 2DEG mobility in the channel under the gate of AlGaN/GaN HEMT devices.In the ASM-HEMT compact model,the effective mobility modeling formula of channel 2DEG under the gate of AlGaN/GaN HEMT devices is developed from the modeling formula of the BSIM3 model,which aimed to Metal Oxide Semiconductor Field Effect Transistor(MOSFET)device modeling,the physical explanation of this modeling formula only considers phonon scattering,interface roughness scattering and Coulomb scattering,In addition,Coulomb scattering is ignored when the carrier density is high since it only dominates when the carrier density is low in MOSFET,the default effective mobility modeling formula of the BSIM3 model does not consider Coulomb scattering,In the subsequent BSIM4 model,users can set the model switch MOBMOD to other values to include Coulomb scattering into the modeling formula.However,there is no similar model switch in the ASM-HEMT model,but a typical effective mobility modeling formula directly used,which leads to not taking Coulomb scattering into consideration.However,AlGaN/GaN HEMTs have a strong polarization effect and are different from MOSFETs.Therefore,the modeling formula that does not consider Coulomb scattering is imperfect.Polarized Coulomb field(PCF)scattering has been proved by a lot of practice,in AlGaN/GaN HEMT devices,PCF scattering is one of the main factors affecting carrier mobility.Therefore,PCF scattering should be included in the modeling formula to make the model more physical.In this paper,the 2DEG mobility of three samples with different gate lengths is calculated by using the self-consistent iteration method,and compared with the 2DEG mobility under the same sample obtained by ASM-HEMT model,it is concluded that PCF scattering is the primary factor for the difference of 2DEG mobility between the two,it further shows that the ASM-HEMT model without PCF scattering is not perfect for AlGaN/GaN HEMT device modeling,and it is necessary to supplement PCF scattering to improve the ASM-HEMT model.3.Devices modeling and performance simulation of GaN-based class A power amplifiers.After the ASM-HEMT model parameters are extracted,only the DUT model can be obtained.However,the actual device will have PADs.Generally,the higher the operating frequency,the more complex the parasitic effect is.Therefore,de-embedding is required to move the electrical reference plane to the DUT.Then,simulate the performance of GaN-based Class A power amplifiers by ADS,the circuit simulation software of Keysight,and obtain important performance parameters of the fabricated AlGaN/GaN HEMT devices.