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 Si₃N₄ single-layer passivation, Al₂O₃/SiN_x bilayer passivation, and ZrO₂/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-SiN_x single layer passivation, including smaller current collapse and higher breakdown voltage. The Al₂O₃/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 V_DS stress of 150 V. On the other hand, the ZrO₂/SiN_x passivated MIS-HEMTs exhibit a higher breakdown voltage of 1207 V, and the dynamic R_on is 1.25 times the static R_on after off-state V_DS stress of 150 V.