Study On Surge Current Capability Of GaN E-HEMTs In The Third Quadrant

As a representative of the third generation of semiconductor materials,GaN has the advantages of wide band gap,high critical breakdown electric field and high electron mobility.Therefore,GaN power devices are capable of building up high-frequency,high-power-density and high-efficiency power conversion systems.GaN enhancement-mode high-electron-mobility transistors（E-HEMTs）,featuring an inherently symmetric lateral channel,can use the same channel to achieve forward and reverse current conduction,which are highly favorable in bidirectional DC/DC converter and DC/RF inter-conversion systems.However,in the above bidirectional conversion systems,especially for high-frequency applications of GaN power devices,the fast switching process is often accompanied by current overshoot/oscillation,which requires GaN E-HEMTs to have a certain surge current capability in the 3^rd quadrant.But so far,the mechanisms of the surge current capability of GaN E-HEMTs which are different from that of PN diodes have not been studied.In this work,based on surge current test,combined with Silvaco TCAD simulation and dynamic gate leakage current（I_G）characterizations,we evaluate the surge current capability of two types of commercial GaN E-HEMTs in the 3^rd quadrant and reveal the impacts of different p-GaN technologies and gate-to-source voltage(V_GS)on surge current capability.The ohmic p-GaN contact and high V_GS,enabling higher efficiency of hole injection and channel modulation,can enhance the surge current capability of GaN E-HEMT in the reverse conduction mode.Furthermore,this work provides optimization schemes to improve the surge current capability of GaN power devices from the aspects of the structure design and application environment.To our best knowledge,it is the first time to investigate the surge current capability,to reveal the underlying mechanisms and to provide optimized solution in lateral GaN power devices.