This work comprehensively investigates device characteristics of a delta-doped In0.45Al0.55As/In0.53Ga0.47As/GaAs metamorphic high-electron-mobility transistors (HEMTs) with different gate alloys, including Ti/Au, Ni/Au, Pt/Au, and Au. The impact-ionization-related kink effects on the device performances are found to be significantly improved by depositing the high-barrier-height gate alloys. As compared to conventional Au-gated metamorphic HEMTs, the devices with Ti/Au, Ni/Au, and Pt/Au gate alloys have shown superior low-noise, high-power, and high-linearity gain performances, respectively. (c) 2006 The Electrochemical Society.