Study Of GaN-Based Vertical Power Devices Based On Electric Field Modulation Technology

In recent years,GaN-based vertical power devices have become an important research subject at home and abroad due to their small chip area,high breakdown voltage and strong current collapse suppression capability.However,the contradiction between breakdown voltage and on-resistance in current GaN-based vertical power devices is still very prominent,especially due to the technical challenge of achieving high p-type doping concentration,resulting the development of GaN-based vertical power device with high breakdown voltage and low on-resistance has great challenges.For above problems,this thesis carries out research work on several new GaN-based vertical power devices.Based on the numerical simulation technology,the working mechanism of each device is analyzed.The influence of structural parameters and material parameters on breakdown characteristics and conduction characteristic are analyzed.And the optimized design of the device structure is made.These results significantly alleviate the contradiction between the breakdown voltage and the on-resistance of the device.Some research results and laws with practical guiding significance are also achieved.The main research work and results of this paper are as follows:CAVET with grooved gate as well as graded Al fraction and uniform-dividing thickness in buffer(GGU-CAVET)and CAVET with grooved gate as well as graded Al fraction and nonuniform-dividing thickness in buffer(GGN-CAVET)are proposed.The influence of device structure parameters on breakdown voltage and on-resistance is simulated,and the working mechanism of the devices is analyzed.The results show that the breakdown voltages of GGU-based CAVET and GGN-CAVET are 2026V and 2173V,respectively,which are slightly higher than those of the traditional SJ CAVET.In addition,the on-resistance of GGU-based CAVET and GGN-CAVET is only 28.6%and 45.4%of the on-resistance in conventional devices,respectively.And the figure of merit(FOM)of the two devices is8.58GW/cm~2 and 6.21GW/cm~2,respectively,which are much higher than those of the traditional devices.Aiming at the bidirectional blocking characteristics of the device,the bidirectional blocking super junction CAVET based on graded AlGaN floating layer(GF-B-SJ CAVET)and the bidirectional blocking super junction CAVET based on dielectric modulation technique(DM-B-SJ CAVET)are proposed and studied.The relationship of device structure parameters and device characteristics is studied.And the device mechanism analysis and optimization design are carried out.The results show that the forward and reverse breakdown voltages of GF-B-SJ CAVET are 3140V and-3115V,respectively,and the FOM is up to4.8GW/cm~2.And the forward and reverse breakdown voltage of DM-B-SJ CAVET are2214V and-2206V,respectively,and the FOM is 2.83GW/cm~2.