In this study, we investigated the impact of intrinsic output conductance (goi) on the short-circuit current-gain cut-off frequency (fT) in InxGa1-xAs/In0.52Al0.48As quantum-well (QW) high-electron-mobility transistors. At its core, we attempted to extract values of fT using a simplified small-signal model (SSM) of the HEMTs and to derive an analytical formula for fT in terms of extrinsic model parameters that are related with intrinsic model parameters of a general SSM. We projected how fT was influenced by goi in HEMTs, emphasizing that the improvement in electrostatic integrity would also be of critical importance to fully benefit from scaling down Lg.