Analysis of Varied Dielectrics as Surface Passivation on AlGaN/GaN HEMT for Analog Applications

In this work, AlGaN/GaN HEMT device performance for different dielectrics as surface passivation have been studied. Due to the high thermal stability, high dielectric constant and high reliability of HfO₂ but limiting interface quality, a stack of silicon nitride with hafnium dioxide has been proposed as surface passivation material for AlGaN/GaN HEMT, attributed to the good interface of Si₃N₄ with GaN. The device performance of AlGaN/GaN HEMTs with various dielectrics i.e. SiO₂, Si₃N₄, Al₂O₃ and a stack of Si₃N₄/HfO₂ as surface passivation layer (SPL) have also been compared using device simulator. Evaluated electrical parameters show that the device passivated with a stack of Si₃N₄/HfO₂ shows high drain current, high breakdown voltage, higher gain as well as higher current switching ratio in comparison with other dielectric materials used as surface passivation, thus the results indicate that the AlGaN/GaN HEMT with stack (Si₃N₄/HfO₂) surface passivation has better device performance suitable for high-power applications.