Small signal modeling of 90 nm gate-length AlGaN/GaN HEMTs considering mesa edge effects

This paper proposes an improved small signal model (SSM) for 90 nm gate-length AlGaN/GaN HEMTs. A mesa edge effect capacitance (CMEE) is introduced into the small signal model to characterize the mesa edge effect. Using scaling formula, the value of CMEE is obtained as 5.1fF. This capacitance makes fT degeneration, especially in small gate-width (Wg) AlGaN/GaN HEMTs. After de-embedding CMEE from AlGaN/GaN HEMTs, the recalculated fT increases 33% with 2×20µm AlGaN/GaN HEMT. The results of our proposed SSM exhibit good agreement with the experimental data of AlGaN/GaN HEMTs with different Wg in our work.