The field modulation effect of fluoride plasma treatment on blocking characteristics of AlGaN/GaN HEMT

We proposed and fabricated AlGaN/GaN HEMTs with highly stable reverse blocking characteristics by 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 a 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 simulated energy band structure and the change of off-state gate drain capacitance. Expanded gate depletion spread E-field more uniformly with reducing field intensity and prevented surface potential from dropping drastically at the gate edge under 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.