Breakdown Mechanism And Structural Optimization Design Of New GaN Power Devices

GaN materials have become a hot spot in the field of power electronics due to their wide band gap and high saturation electron velocity.GaN-based HFET devices are attracting more and more attention in the high-power field due to their ability to form high-density,high-mobility two-dimensional electron gas.However,there are two major problems with GaN HFET devices:the concentration of the electric field at the drain edge of the gate causes the device to breakdown prematurely;the device implements an enhanced method with drawbacks.Considering the above two problems,this paper has carried out further research based on the work of the predecessors.In terms of the problem of the electric field concentration at the drain edge of the gate causes the device to breakdown prematurely in the GaN HFET.In this paper,we innovatively proposed a GaN HFET device with a dipole layer(GaN DL-HFET).By introducing an AlxGa1-xN(0<x<0.28)dipole layer having a polarization intensity lower than the barrier layer in the passivation layer between the gate and drain to modulating the distribution of electric field along the channel,the electric field peak at the drain edge of the gate is lowered and improve the electric field along the channel between the gate and the drain.So the electric field distribution is more uniform,achieving the purpose of improving the breakdown voltage of the device.The parameters of the dipole layer are optimized based on the standard of obtaining higher power figure FOM.The breakdown voltage of GaN DL-HFET is 1130V,which is 128%higher than the 496V of the conventional GaN HFET device.The on-resistance of the GaN DL-HFET is 0.48m?.cm~2,compared with the conventional GaN HFET,only increased by 0.07 m?.cm~2.At this time,the FOM is up to 2.67 GW/cm~2.At the same time,the device cut-off frequency maintained a high level of 32.4 GHz.Different from the field plate structure,GaN DL-HFET devices do not introduce parasitic capacitance significantly while significantly increasing the withstand voltage of the device,maintaining good frequency characteristics.These results demonstrate the potential to achieve high breakdown voltage while maintaining low on-resistance and good frequency characteristics,demonstrating great potential in power electronics applications.In view of the current demand for enhancement-mode GaN HFET in integrated circuits,a GaN HFET with a composite barrier layer(GaN CBL-HFET)was proposed in this paper.Based on the polarization effect of the nitride material and the depletion of two-dimensional electron gas by P-type doping,by embedding a P-type AlxGa1-xN(0<x<0.28)having a polarization intensity lower than other regions of the barrier layer in the barrier layer below the gate,the device is enhanced by depleting the two-dimensional electron gas under the gate.Compared with the threshold voltage of-1.88V of the conventional GaN HFET,the threshold voltage of 1.91V is realized by optimizing the structural parameters of in CBL GaN CBL-HFET,and an enhancement-mode GaN HFET is realized.