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

In this paper, the GaN-based MIS-HEMTs with Si ₃ N ₄ single-layer passivation, Al ₂ O ₃ /SiN _x bilayer passivation, and ZrO ₂ /SiN _x bilayer passivation are demonstrated. High-k dielectrics are adopted as the passivation layer on MIS-HEMTs to suppress the shallow traps on the GaN surface. Besides, high permittivity dielectrics passivated MIS-HEMTs also show an improved breakdown voltage characteristic, and that is explained by 2-D simulation analysis. The fabricated devices with high-k dielectrics/SiN _x bilayer passivation exhibit higher power properties than the devices with plasma enhanced chemical vapor deposition-SiNx single layer passivation, including smaller current collapse and higher breakdown voltage. The Al ₂ O ₃ /SiN _x passivated MIS-HEMTs exhibit a breakdown voltage of 1092 V, and the dynamic R _on is only 1.14 times the static R _on after off-state VDS stress of 150 V. On the other hand, the ZrO ₂ /SiN _x passivated MIS-HEMTs exhibit a higher breakdown voltage of 1207 V, and the dynamic Ron is 1.25 times the static R _on after off-state VDS stress of 150 V.