Decrease in on-state gate current of AlGaN/GaN HEMTs by recombination-enhanced defect reaction of generated hot carriers investigated by TCAD simulation

Abstract

Changes in the on-state gate current of AlGaN/GaN high-electron-mobility transistors (HEMTs) under various electrical and thermal stress conditions have been analyzed by technology computer-aided design (TCAD) simulation. A larger gate current is observed under on-state bias condition than that under off-state bias condition. The TCAD simulation indicates that on-state gate current flows from the heated gate electrode to the AlGaN layer by tunneling or hopping through the gate depletion layer when we apply some deep-donor-type traps under the gate in the AlGaN barrier layer. The gate current is caused by electrons that flow and is pulled away by the applied gate-to-drain voltage under a high channel temperature condition. The deep traps benefit both the on- and off-state gate current behavior. We found that the on-state gate current is effectively decreased by electrical stress under the on-state condition. Electroluminescence measurement indicates that a large number of hot carriers are generated under this condition. The results suggest that the process-induced crystal defects are annealed out by non-radiative recombination of the generated hot carriers by a recombination-enhanced defect reaction mechanism. The change in the on-state gate current in the TCAD simulation can be successfully explained by the decrease in the donor traps.