Fabrication And Simulation For Performance Optimization Of Gallium Nitride Semiconductor Devices

Gallium nitride(GaN)is the third-generation wide-bandgap semiconductor material.It possesses excellent characteristics such as high electron mobility,high breakdown voltage,low on resistance,fast switching frequency and high temperature workable performance,was making it being favored for the high voltage power switch application.AlGaN/GaN schottky barrier diode(SBD)has become a focus of the research of GaN devices based on the study of the current GaN high electron mobility transistor(HEMT).This thesis was based on Silvaco TCAD simulation software to simulated and analyzed AlGaN/GaN SBD.At the same time,this paper proposed a new type of AlGaN/GaN P-GaN diode structure.Finally,AlGaN/GaN SBD and AlGaN/GaN P-GaN were prepared,tested and analyzed,simulation results and verification results were verified,and high-performance GaN diode devices were finally obtained.The main research results of this paper were as follows:(1)The structure of AlGaN/GaN SBD device was optimized and simulated.Based on SILVACO TCAD simulation tool,the basic structure of AlGaN/GaN SBD device was simulated.By adjusting different structural parameters of AlGaN/GaN SBD device,the effects of structural changes such as Al component change,electrode spacing,field plate structure,passivation layer thickness under field plate and field plate length on electrical performance are studied.The results showed that the performance of AlGaN/GaN SBD was the best when the Al component was 0.25,the distance between anode and cathode was 10 μ m,the thickness of passivation layer under field plate was 0.5 μm and the length of field plate was 3 μm.(2)Based on the structure of the AlGaN/GaN SBD device and guided by the unidirectional conductivity of the PN junction,a new type of AlGaN/GaN P-GaN diode was designed and simulated.At the same time,the influence of structural parameter changes of AlGaN/GaN P-GaN diode devices on the device performance was studied,and the structural changes of P-type GaN thickness,field plate structure,field plate height and field plate length were analyzed.The results showed that the AlGaN/GaN P-GaN diode has the best performance when the thickness of the P-type GaN layer was 0.2 μm,the height of the field plate was 0.7 μm,and the length of the field plate was 3 μm.At the same time,compared with the best simulated AlGaN/GaN SBD device structure,it was found that the AlGaN/GaN PGaN diode has better reverse characteristics and has broad application prospects in the field of high-voltage and high-power switches.(3)Complete AlGaN/GaN SBD and AlGaN/GaN P-GaN devices were constructed based on the optimized GaN structure parameters.The effects of field plate height and length on the performance of two GaN devices were studied,the experimental results and simulation results were compared and analyzed,and the accuracy of the simulation results was discussed.The results showed that with the increase of the field plate height,the breakdown voltage first increases and then decreases.The AlGaN/GaN SBD achieves the maximum breakdown voltage of-972 V at 0.5 μm,and the AlGaN/GaN P-GaN achieves the maximum at 0.7 μm.The breakdown voltage was-1105 V,with the increase of the field plate length,the breakdown voltage of AlGaN/GaN SBD increases from-650 V to-972 V,and the AlGaN/GaN P-GaN increases from-765 V to-1108 V.When the length of the field plate of the device continues to increase,the breakdown voltage basically does not change.This law verifies the conclusion obtained by the simulation and has guiding significance for the structural optimization of the device.