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Significant progress has been achieved in making larger (2 inch) 4H-SiC substrates with much lower micropipe defect densities. With the recent availability of semi-insulating 4H-SiC substrates, the demonstration of impressive microwave power results have been made possible both in SiC MESFETs and in GaN/AlGaN HEMTs grown on these substrates. SiC MESFETs have achieved RF power densities of 4.6 W/mm and 4.3 W/mm at 3.5 GHz and 10 GHz, respectively. The largest total RF output power from a single MESFET is 80 watts CW at 3.1 GHz. GaN/AlGaN HEMTs fabricated on these substrates have demonstrated a record 6.9 W/mm at 10 GHz, and a total RF output power of 9.1 watts CW at 7.4 GHz .