This Phase-II SBIR proposal proposes for the first time ever, the use of a new class of materials - Gallium Nitride-on-diamond - in the manufacture of very high power, high-temperature, Ka-band solid-state MMICs. In this particular Phase-II, the first ever 34-38GHz GaN-on-Diamond FETs will be demonstrated, exhibiting a record 5-10 W/mm at record efficiency and temperature levels. Arrays of these FETs will be used to form (power combined) 10KWatt Power Amplifiers (PA) MMICs. Polycrystalline free standing CVD diamond nature's most efficient thermal conductor enables nearly perfect heat extraction from a "hot" device (Thermal conductivities of GaAs, Si, and SiC are 35W/m/K, 150W/m/K and 390W/m/K respectively; diamond ranges from 1200-2000 W/m/K depending on quality). In the proposed scheme, the device's active epitaxial layers are removed from their original substrate and transferred to a specially treated low-cost CVD diamond substrate using a proprietary low-cost manufacturable scheme. The active junction rests just 20-nm from diamond. The semiconductor-on-diamond technology proposed here may be applied to GaAs, SiC, SiGe, etc. at up to 8" in wafer diameter.