Effect of Gate Leakage in the Subthreshold Characteristics of AlGaN/GaN HEMTs

Abstract
This letter studies the effect of gate leakage on the subthreshold slope and ON/OFF current ratio of AlGaN/GaN high-electron mobility transistors (HEMTs). We found a strong correlation between the gate leakage current and the transistor subthreshold characteristics: the lower the gate leakage, the higher the ON/OFF ratio and the steeper the subthreshold slope. To improve the subthreshold characteristics in GaN HEMTs, the gate leakage current was reduced with an O2 plasma treatment prior to the gate metallization. The O2 plasma treatment effectively reduces the gate leakage current by more than four orders of magnitude, it increases the ON/OFF ratio to more than seven orders of magnitude and the improved AlGaN/GaN HEMT shows a nearly ideal subthreshold slope of 64 mV/dec.

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