Ultra-wide bandgap (AlN, diamond, Ga 2 O 3 ) have attracted significant research interest for high power and high frequency applications. Al rich (> 60%) AlGaN channel heterojunction field effect transistor (HFET) is a promising candidate for high power RF devices due to the large bandgap, high breakdown field and compatible saturation velocity with GaN. Consequently, Al rich (>60%) AlGaN channel transistors have been explored [ 1 – 8 ] . The AlGaN channel (Al > 60%) transistors have demonstrated good unity gain frequency (f T ) performance (~40 GHz) and decent breakdown voltage (~45 V) [6] . However, short channel effects in Al rich (Al > 60%) transistors due to a reduced gate length between 80nm–150nm limited the high breakdown voltage performance demonstration with >10 GHz f T for Al rich (Al > 60%) AlGaN channels [6 , 7] . In this work, we demonstrate high frequency (fT > 17 GHz) and high breakdown voltage (>360 V, >150 V/μm) simultaneously for 64% AlGaN channel transistors.