Metamorphic HEMT (MHEMT) structures on As, Sb, and P-based buffers with different grading profiles were grown by molecular beam epitaxy. Structural, electrical, and optical characterization were used to correlate buffer layer design and growth parameters with channel carrier mobility, surface morphology, and photoluminescence efficiency. All MHEMTs studied in this work exhibited excellent transport properties comparable to reference HEMT grown lattice-matched on InP. RMS roughness of <14 Å were achieved for both InAlGaAs and AlGaAsSb-based buffers. MHEMT devices with 0.15? m gates was fabricated successfully with transconductance of 710 mS/mm, maximum current of 500 mA/mm, and gate-drain breakdown of 5 V.