Simulation Research On Mechanism Of High Voltage And Low Loss GaN Based Power Devices

Power semiconductor devices are the cornerstone of modern power electronics technology.Power devices with excellent performance and high reliability are the key to improve the efficiency of power conversion systems,providing support for the realization of new application scenarios and the decrease in carbon emission for existing demand,which can effectively improve social and economic benefits and promote the"Emission Peak"and"Carbon Neutrality".As a typical representative of the third generation semiconductor materials,Gallium Nitride(GaN)has the advantages of high critical breakdown electric field,high electron saturation speed and strong irradiation resistance,etc.It has been widely used in microwave/RF,mobile communication,power electronics and photoelectric lighting.In the field of power electronics,relying on the high carrier concentration and high mobility brought by the polarization effect of heterojunction structure,GaN power devices have received a lot of attention from academia and industry with multiple improvements in power GaN techniques already.However,there are still many technical problems that hinder the further implementation of GaN devices.In this thesis,a novel AlGaN/GaN HEMT is proposed and analysed through Sentaurus TCAD simulation.Key processes experiments including fluorine ion implantation are conducted,followed by actual device fabrication and characterization.A double heterojunction enhanced MIS-type Hybrid-Anode diode device is also proposed,and the device is analysed and optimized based on Sentaurus TCAD.This thesis provides the following contributions:1.An enhanced high-voltage AlGaN/GaN HEMT device with multiple fluorine implanted region is proposed and fabricated.The fluorine implanted region is divided into a gate region and a termination region.With a single step implantation on locally thinned passivation layer,both the gate enhancement and the multi-region fluorine implanted termination are realized.The passivation layer acts as a protection layer for ion implantation,effectively improving the interface quality and reducing the concentration of interfacial traps.The multi-region ion implanted termination modulates the surface electric field distribution in the drift region and optimizes the figure of merit between on-state resistance and breakdown voltage.Test results show that the multi-region fluorine ion implantation termination improves the figure of merit by 63%to 696MW/cm~2.2.A recessed MIS-type hybrid anode diode with Polarization Super Junction structure is proposed.Two-Dimensional Hole Gas and Two-Dimensional Electron Gas are formed at p-GaN/Al GaN/GaN double heterojunction,introducing charge balance in drift region for an optimized electric field distribution under reverse bias condition,which can increase the breakdown voltage of the device.Conventional Schottky contact is replaced by recessed MIS hybrid anode structure for lower turn-on voltage of the diode.The simulation results show that the new device has a low turn-on voltage of 0.4V,an increase of 104%in output current and an average electric field of 1.86MV/cm in drift region.