Investigation Of The Threshold Voltage Instability In Normally-Off P-Gan/Algan/Gan Hemts By Optical Analysis

A normally-off p-GaN/AlGaN/GaN high-electron-mobility transistor (p-GaN HEMTs) with a semitransparent gate electrode was investigated. Under forward gate bias, electroluminescence (EL) emission was observed which demonstrated the hole injection in the gate heterostructure. The hole injection emerged at a gate bias of 3.5 V and was significantly enhanced when the gate bias was larger than 6 V, the corresponding EL emission intensity was increased by approximately 100 times. It was also found that the electron injection and trapping in the p-GaN resulted in the threshold voltage (V (TH)) instability of the p-GaN HEMTs, while the hole injection resulted in the electron-hole recombination and the suppression of electron trapping. The carrier injection dynamics in the p-GaN gate region were quantitatively identified at different temperatures. Finally, the GaN band-edge ultraviolet emission with an energy of 3.4 eV was demonstrated as the most effective component in EL emission for V (TH) instability suppression in the p-GaN HEMTs.