Fermi-Level Pinning Effect in Gate Region: A Case Study of Multimetal Gated AlGaN/GaN HEMT for High RF Linearity

This work investigates the robustness of AlGaN/GaN multimetal gated (MMG) HEMT architecture for third-order transconductance (g
m3
) optimization and linearity improvement in the presence of Fermi-Level pinning (FLP). Through Technology Computer-Aided Design (TCAD), Compact modeling and Load-Pull simulations, it is shown that despite incorporating FLP, employing MMG scheme improves device level g
m3
-suppression leading to an improvement in output-referred third-order intercept point per unit DC power (OIP3/P
dc
) and third order intermodulation distortion (IMD3). Remarkably, OIP3/P
dc
of 18.9 dB is obtained considering an FLP factor of 0.43, which is 10.7 dB improvement than the conventional planar HEMT. A comparative analysis on output power back-off (OBO) for conventional and MMG HEMT with different FLP factors establishes MMG as a robust architecture to FLP, and therefore a practical method to enhance linearity of GaN power amplifiers.