The development of the 100×4 micron transistor design, the nano-structured hetero-layered materials and the technology with 0.15 to 0.2 micron design rules has made possible the production of power GaN/AlGaN Ka-band HEMT's on silicon carbide substrates and measurements of their static and ultra-high-frequency characteristics (S-parameters). The HEMT parameters Gmax=8.89 dB and Pout∼ 450 mW achieved at frequencies up to 40 GHz indicate the possibility of using them for creation of the SSI Ka-band power amplifiers.