Study And Design Of Novel Vertical GaN-based Power Devices With High Breakdown Voltage

Recently,vertical GaN-based power devices have become one of the most important research branches in the field of power electronics,due to their reduced chip area,the packaging convenience and the excellent suppression of current collapse.And it has been one of the research focuses in vertical GaN-based power devices to further improve the trade-off characteristic between the breakdown voltage and the specific on-resistance.Aiming at the on-state and off-state performance of vertical GaN-based power devices,the emphasis is put on the studies of the innovation of device structures,the analyses of the operation mechanism and so on.Many research results and lows with practical value are achieved.Main research works and achievements are in the following.A vertical GaN-based power device with nonuniform doping superjunctions is proposed.The relationships between nonuniform doping superjunctions and breakdown voltage as well as specific on-resistance are investigated systematically.The inherent device physical mechanism is revealed.And the optimization designs of device structure are performed.Compared with the conventional vertical GaN-based power device with superjunctions?SJ CAVET?which has the same breakdown voltage,the reduction in specific on-resistance of this novel device could be 51%.A vertical GaN-based power device with step-doping superjunctions is proposed and studied.The trade-off of the breakdown voltage and the specific on-resistance is improved obviously.Compared with the conventional SJ CAVET,the 30%enhancement of breakdown voltage and the 10.6%decrease in the corresponding specific on-resistance could be achieved in the device with three doping parts.Moreover,the specific on-resistance could be further reduced by adding the number of the doping layers in n-and p-pillars,with little degradation of breakdown voltage.A novel vertical GaN-based power device with drain-connected semi-superjunctions is investigated,aiming at the reverse blocking ability.A reverse breakdown voltage of-3920V could be obtained in device with the buffer doping concentration of 3.5×10¹⁶cm^-3.In addition,the effect of the structure parameters of drain-connected semi-superjunctions on the reverse breakdown voltage and the specific on-resistance is studied by simulations.And the inherent mechanism of the drain-connected semi-superjunctions to improve the reverse blocking performance is analyzed.A vertical GaN-based power device with drain-connected floating-superjunctions is presented.A forward breakdown voltage of 3549V and a reverse breakdown voltage of-3562V could be achieved in device where the distance T_up between the P-pillar and the CBL is 3.4?m,resulting in the excellent bidirectional blocking abilities.The relationship of the on-state performance,the bidirectional blocking performance and device structure parameters is analyzed by numerical simulations.And the physical mechanism of the drain-connected floating-superjunctions to improve the bidirectional blocking performance is revealed.The results and laws with the practical value are obtained.