0.25 m Ga N HEMT with Al Ga N back barrier for high power switch application has been presented. By introducing Al Ga N back barrier, the buffer layer breakdown voltage for the metal-organic chemical vapor deposited Al Ga N/Ga N hetero-structure on 3-inch Si C substrate showed a considerable increment, which was nearly 4 and2 of that for the conventional Ga N buffer layer and Ga N buffer layer with Fe doped, respectively. Ga N switch HEMTs with source to drain spacing of 2, 2.5, 3, 3.5 and 4 m were fabricated on the Al Ga N/Ga N epitaxial material with Al Ga N back barrier and estimated off state power handling for the Ga N switch HEMTs were 25.0, 46.2, 64.0,79.2, and 88.4 W, respectively. A demonstrator DC–12 GHz Ga N SPDT MMIC switch was designed in reflective series-shunt-shunt configuration based on the Ga N HEMT, with a source to drain spacing of 2.5 m. The developed SPDT MMIC switch showed a maximum insertion loss of 1.0 d B and a minimum isolation of 30 d B at a frequency range of DC–12 GHz. A power handling capability of 44.1 d Bm was achieved at 10 GHz for the MMIC switch with continuous wave power compression measurement. 0.25 m Ga N HEMT with Al Ga N back barrier for high power switch application has been presented. By introducing Al Ga N back barrier, the buffer layer breakdown voltage for the metal-organic chemical vapor deposited Al Ga N / Ga N hetero-structure on 3-inch Si C substrate showed a considerable increment, which was nearly 4 and 2 of that for the conventional Ga N buffer layer and Ga N buffer layer with Fe doped, respectively. Ga N switch HEMTs with source to drain spacing of 2, 2.5 , 3, 3.5 and 4 m were fabricated on the Al Ga N / Ga N epitaxial material with Al Ga N back barrier and estimated off state power handling for the Ga N switch HEMTs were 25.0, 46.2, 64.0, 79.2, and 88.4 W, respectively. A demonstrator DC-12 GHz Ga N SPDT MMIC switch was designed in reflective series-shunt-shunt configuration based on the Ga N HEMT with a source to drain spacing of 2.5 m. The developed SPDT MMIC switch showed a maximum insertion loss of 1.0 d B and a minimum isolation of 30 d B at a frequency rang e of DC-12 GHz. A power handling capability of 44.1 d Bm was achieved at 10 GHz for the MMIC switch with continuous wave power compression measurement.