Effect of High-k Passivation Layer on Electrical Properties of GaN Metal-Insulator-Semiconductor Devices

In this paper, a 2-D simulation of breakdown characteristics of GaN-based Metal Insulator Semiconductor High Electron Mobility Transistors with a high permittivity passivation layer was performed. As a result, it is found that the breakdown voltage is enhanced with permittivity of the passivation layer due to reduction of the electric field at the drain edge of gate. In addition, the GaN-based MIS-HEMTs with three different passivation (Si 3 N 4 passivation, Al 2 O 3 /SiNx stack passivation and ZrO 2 /SiNx stack passivation) were fabricated and compared. The breakdown voltage of the MIS-HEMTs passivated with ZrO 2 /SiNx stack is 483 V, which is 22% higher than for the MIS-HEMTs with Si 3 N 4 passivation. Moreover, the devices passivated with SiNx or bilayer Al 2 O 3 /SiNx show significant current collapse (~33% and ~8%, respectively), while the bilayer ZrO 2 /SiNx passivated devices exhibit negligible current collapse of ~1%.