Improved DC-RF dispersion with epitaxial passivation for high linearity graded AlGaN channel field effect transistors

We demonstrate DC-RF dispersion-free graded AlGaN channel transistor with an epitaxial passivation. The device used for this experiment was an AlGaN channel polarization-graded field effect transistor (PolFET) with Al-composition grading from 0% to 30%. We were able to reduce the dispersion to almost zero current collapse and zero knee-walkout for pulsed I-V up to 30 V drain quiescent bias condition with epitaxial passivation, compared to 8 V knee-walkout and 25% current collapse for PolFETs with traditional PECVD SiNx for the same measure conditions. We also report large signal power density and two-tone linearity for these devices up to X-band frequencies. (C) 2020 The Japan Society of Applied Physics