High breakdown voltage AlGaN/GaN HEMT by employing selective fluoride plasma treatment

We proposed and fabricated AlGaN/GaN HEMT with high stable reverse blocking characteristics employing fluoride plasma treatment using CF₄ gas. The plasma treatment with various rf power was performed selectively on drain-side gate edge region where electric field was concentrated. Unlike normally-off process, fluoride plasma treatment with attenuated RF power expanded gate depletion region in the direction of drain electrode. Expansion of depletion was confirmed by the change of measured off-state gate-drain capacitance. Expanded gate depletion spread E-field more uniformly with reducing peak of field intensity and prevented from drastic surface potential drop at the gate edge under large reverse bias condition. By the mitigation of field concentration and gradual potential change due to plasma treatment, was leakage current reduced and high breakdown voltage achieved. The breakdown voltage of plasma treated device with optimized rf power was 1400 V while that of untreated sample was 900 V. The leakage current of plasma treated device was 9.5 nA.