High-performance metamorphic Al0.49In0.51As-/Ga0.47-In0.53As high-electron-mobility transistors (mHEMTs) grown on Si substrates by metal-organic chemical vapor deposition (MOCVD) using an effective multistage composite buffer scheme have been fabricated. Room-temperature Hall measurements show an average sheet carrier density of 4.5 × 1012 cm-2 with a mobility of over 7500 cm2/V·s. Maximum transconductance of mHEMTs with a 100-nm gate length was ~ 770 mS/mm, which is nearly the same as that of mHEMTs with the same dimension grown on GaAs substrates by MOCVD. The unity current gain cutoff frequency (fT) and the maximum oscillation frequency (fmax) were 210 and 146 GHz, respectively. To our best knowledge, these results are the best reported for MOCVD-grown mHEMTs on Si.