All MOCVD grown 250 nm gate length Al0.70Ga0.30N MESFETs

Abstract

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 $\mathrm{UWBG}\ \mathrm{A}10. 70\mathrm{Ga}0.30\mathrm{N}$ MESFET with $\mathrm{L}_{\mathrm{G}} =250\ \ \mathrm{nm}$.