All MOCVD grown 250 nm gate length Al 0.70 Ga 0.30 N MESFETs

High Al-composition AlGaN materials, by virtue of their ultra-wide band gap, are promising candidates for realizing high power density mm-wave transistors. However, low electron affinity in these materials make it very difficult to make ohmic contacts for Al-composition above 65%. On the other hand, to achieve high cutoff frequency, it is critical to scale the transistors. In this work, we report the first ever DC and small-signal RF performance of a scaled MOCVD-grown $mathrm{UWBG} mathrm{A}10. 70mathrm{Ga}0.30mathrm{N}$ MESFET with $mathrm{L}_{mathrm{G}} =250 mathrm{nm}$ .