Characteristic Simulation Of AlGaN/GaN HEMT Devices

As a third-generation semiconductor material,gallium nitride(GaN)has outstanding advantages such as wide band gap,high electron drift velocity,high thermal conductivity,high breakdown electric field,high heat resistance,and high radiation resistance.These characteristics make GaN an excellent material for manufacturing high temperature,high voltage,high power,radiation resistant semiconductor devices.Gallium nitride-based high electron mobility transistor(GaN HEMT)has high channel electron concentration,extremely high electron mobility and high breakdown voltage,which makes it have great development prospect in high frequency and microwave.At the same time,GaN HEMT can be grown on a large-sized Si substrate to provide high performance and low price,making it an ideal power switching device.The key to the excellent performance of GaN HEMTs is the high-density two-dimensional electron gas generated by the AlGaN/GaN heterojunction,and the composition of the heterojunction has an extremely important influence on the concentration of the two-dimensional electron gas and various characteristics of the device.In the development of GaN HEMT,increasing the breakdown voltage and suppressing current collapse has been the focus and difficulty of research.This paper was completed with the support of the National Science and Technology Major Project(No:2017YFB0402800,2017YFB0402803).The main research work and achievements of this paper are as follows:Firstly,this paper explained the study of researching the improvement mechanism of the breakdown voltage of the field plate structure.The simulation results verify the effect of the field plate structure.Then,it was proved that the breakdown voltage of the device can be inceased by optimizing the thickness of the oxide layer,the length of the field plate and the thickness of the field plate based on the field plate structure,which also make the device obtained the best field plate structure parameters.Secondly,this paper also showed the the influence of the change of the Al composition of the barrier layer in the AlGaN/GaN heterojunction of GaN HEMT on the device,and the effects on various characteristics through simulation,including the two-dimensional electron gas concentration at the heterojunction interface,twodimensional electron gas mobility,heterojunction band width,and transfer characteristics,output characteristics,breakdown characteristics,and the like.The effects of Al composition changes were explored from various angles,and the respective advantages of high and low Al composition heterojunctions were analyzed.Finally,this paper introduced and tested the difference between enhanced GaN HEMT and depletion GaN HEMT,and verified the methods of fabrication of enhanced devices such as thin barrier,trench gate,F-ion implant and P-type GaN gate.The current collapse and its formation model are studied in the paper.The simulation results are verified for the field plate structure,double channel structure,HD-GIT drain structure and optimized production process which can suppress current collapse.The current collapse of the enhanced GaN HEMT has been fully verified from the phenomenon,principle,model and suppression method.