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 O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> plasma treatment prior to the gate metallization. The O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> 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.