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This letter presents the RF power performance of N-polar AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MISHEMTs) grown by metal-organic chemical vapor deposition (MOCVD) on semi-insulating SiC substrates at 10 and 4 GHz. Additionally, an Al2 O3-based etch-stop technology was demonstrated for improving the manufacturability of N-polar GaN HEMTs with SixNy passivation. The reported output power densities of 16.7 W/mm at 10 GHz and 20.7 W/mm at 4 GHz represent the highest reported values so far for an N-polar device, at both of these frequencies. The improvements achieved in the RF output power density when compared with previously reported N-polar MISHEMTs can be attributed to high breakdown voltage of N-polar devices grown by MOCVD and high thermal conductivity of the SiC substrate.