Simulation And Fabrication Of GaN Power Device With High-? Gate Dielectrics

With the vigorous development of 5G,consumer electronics,new energy vehicles,smart grids and other fields,the demand for power devices is increasing.With many advantages such as high breakdown voltage,high carrier mobility,and low on-resistance,Gallium Nitrogen(GaN)power devices are on the cusp of the times.As the focus of research on GaN power devices,AlGaN/GaN heterojunction HEMT devices have been studied for nearly 30 years,and their performance has been continuously optimized,but there are still some problems that need to be resolved.In this paper,the recessed gate GaN MIS-HEMT structure based on the high dielectric constant HfSiO dielectric can realize enhancement mode GaN devices,improve device leakage,and increase breakdown voltage.First,Sentaurus was used to simulate depletion mode and recessed gate enhancement mode GaN MIS-HEMT.From the energy band diagram and transfer characteristic curves obtained by simulation,the recessed gate structure has realized the transition of the device from the depletion mode to the enhanced mode.Taking into account of the self-heating effect of GaN power devices,a thermodynamic model was used,and the phenomenon of negative differential resistance(NDR)was observed from the simulation results,and the lattice temperature of the device can be analyzed by simulation.In addition,the breakdown characteristics of the device in the off state were also simulated.The simulation results can provide theoretical guidance for subsequent experiments.Then,GaN MIS-HEMT devices based on high-?dielectric were fabricated.The recessed gate adopted the atomic layer etching method and the etching depth is controllable with low surface.The source and drain electrodes adopted the process of Ti/Al/Ni/Au and the low-temperature Au-free process of Al/Ti N,both of which can realize the ohmic contact of the device.The gate dielectric useed the atomic layer deposition(ALD)method to grow a high-quality HfSiO dielectric.The results of the electrical characterization of the recessed gate GaN MIS-HEMT show the on-off ratio of the device up to 10¹⁰,the specific on-resistance of 5.4 m?·cm²,and the breakdown voltage up to 1200 V.Finally,a multi-finger recessed gate GaN MIS-HEMT device was fabricated,with a device size of 3 mm×3 mm and a total gate width of 120 mm.Compared with the small-size GaN device process,multi-finger bridging and electroplating processes were added.The electrical characterization results show the maximum saturated output current of the device reaching 26 A,the on-resistance of 150 m?,and the breakdown voltage of 125 V.