Simulation Of High Voltage AlGaN/GaN HFET

AlGaN/GaN heterojunction field-effect transistors(AlGaN/GaN HFETs)have high breakdown voltage,high electron mobility and low on-resistance,which have become the focus of research at home and abroad.However,the breakdown voltage of GaN power devices is far from the theoretical limit.How to improve the breakdown v oltage of AlGaN/GaN HFET devices without affecting other characteristics as little as possible is an urgent problem to be solved.This paper focuses on the realization of high breakdown voltage of AlGaN/GaN HFET devices.The main research contents and achievements are as follows:In this paper,the research background,development process and development direction of AlGaN/GaN HFET are s?mmarized at first,and then the polarization effect of III-V compound semiconductor and the origin of two-dimensional electron gas are described in detail,and then the current and voltage characteristics and working principle of AlGaN/GaN HFETs are explained.In this paper,an AlGaN/GaN HFET with a polarization layer below gate is proposed and studied.The mechanism of the polarization layer structure to improve the breakdown voltage is analyzed,that is,the distribution of polarization charge under the gate is modulated by the polarization layer structure,and then the distribution of channel electric field is modulated effectively,and the breakdown voltage of the device is improved.Furthermore,the structure is optimized and simulated,and the influence of different polarization layer thickness and Al component on the channel electric field distribution and on-resistance is analyzed,and then the optimal structural parameters are obtained.Finally,the effect of polarized layer structure on the conduction and transfer characteristics of the device is studied.The addition of polarized layer will reduce the saturation curr ent density of the device and increase the on-resistance of the device,which indicates that the polarized layer structure sacrifices the current capacity to some extent to improve the breakdown voltage,but this is in line with the principle of compromise in the design of power device.According to the simulation results,the on-resistance of the device is increased from 0.61m??cm~2 to 1.02 m??cm~2,and the breakdown voltage of the devices change from 209.8V to1195V.The performance of the device has been greatly improved.The mechanism of the field plate structure improving the breakdown voltage of the device is studied in chapter four.In addition,different field plate structures,such as gate field plate,discontinuous field plate and double deck field plate,were simulated and compared,and relevant structural parameters were optimized.Then,the polarization layer below gate was combined with the field plate structure,and the channel electric field distribution was further optimized,also the breakdown voltage of the device is improved.According to the simulation results,the device with the polarization layer below gate and the gate field plate can obtain a high breakdown voltage of 1630V at a gate-to-drain spacing of12?m.