Research On Withstand Voltage And Polarization Characteristics Of Vertical GaN HEMT Devices

In this paper,compared with the lateral GaN HEMT(High Electron Mobility Transistor)device,the vertical GaN current aperture transistor(Current Aperture Vertical Electron Transistor,CAVET)is more convenient for packaging and testing,reducing the chip area,and it has more advantages in terms of breakdown electric field and suppression of current collapse effect.The voltage withstand characteristics,conduction characteristics and polarization characteristics of GaN CAVET devices are studied from the following three aspects:(1)Research on power characteristics of GaN CAVET devices:for GaN power devices,it is necessary to obtain lower on resistance and higher breakdown voltage at the same time,which puts forward new requirements for device materials and structures,which need to be further studied and discussed;(2)Research on enhanced CAVET devices:normally off devices are more conducive to simplify circuit design and achieve low power consumption,so it is necessary to study vertical GaN enhanced devices;(3)Research on dual channel CAVET device:due to special structural characteristics,the vertical device increases the on resistance,so the output current is smaller than the horizontal device,so the vertical device with high output current is studied.In this paper,Sentaurus TCAD simulation software is used to simulate GaN CAVET device,and the device performance under different structure and material parameters is explored.Through the optimization of device simulation model and structure parameters,better device performance is obtained.Aiming at the problem of insufficient withstand voltage of the buffer layer of the traditional GaN CAVET structure,a graded-step buried GaN vertical device(GPBL-GaN CAVET)is proposed based on the theory of the buried layer structure and the superjunction structure.By optimizing the device structure and process parameters,the result shows that the off-state breakdown voltage of the GPBL-GaN CAVET is 2536 V,which is 989 V higher than the breakdown electric field of the traditional structure device,which is an increase of64%,and the on-resistance is 1.95 m?·cm².The value of FOM is 3.22 GW/cm²,which is a148%improvement over the performance of the traditional device.In order to solve the problem that the buffer layer of traditional GaN CAVET has large leakage current and is difficult to realize enhanced device,based on the Si O₂ current barrier layer(CBL)structure,a polarization modulation engineering CAVET(PE-CAVET)—Si O₂-AlN hybrid barrier layer(HCBL)enhanced Al_0.3Ga_0.7N/GaN is discussed.Because of the two-dimensional hole gas(2DHG)formed from GaN/AlN heterojunction,the threshold voltage of Si O₂-AlN HCBL CAVET is 2.31 V,the current switching ratio is 10¹²,and the breakdown voltage is 864 V.Compared with the traditional GaN CAVET,the withstand voltage is increased by 156%and the leakage current is reduced by 4 orders of magnitude;To solve the problem of low output current of traditional single channel Si O₂ CBL CAVET,the Si O₂-In_0.05Ga_0.95N HCBL Al_0.3Ga_0.7N/GaN is proposed.A two-dimensional electron gas(2DEG)subchannel formed by GaN/InGaN heterojunction is introduced to enhance the saturation output current of the device.The saturation output current of the device is 985m A/mm and the transconductance is 256 m S/mm.Compared with single channel Si O₂ CBL CAVET,the saturation output current and transconductance of device are increased by 30% and 25%,respectively.