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 (C_MEE) is introduced into the small signal model to characterize the mesa edge effect. Using scaling formula, the value of C_MEE is obtained as 5.1fF. This capacitance makes f_T degeneration, especially in small gate-width (W_g) AlGaN/GaN HEMTs. After de-embedding C_MEE from AlGaN/GaN HEMTs, the recalculated f_T 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 W_g in our work.