Investigation of gate conduction mechanisms in p-NiO gate HEMTs with a type-II band aligned NiO/AlGaN heterojunction

In this Letter, the effect of post-metallization annealing (PMA) on the gate conduction mechanisms of p-NiO gate AlGaN/GaN high electron mobility transistors with a NiO/AlGaN type-II band alignment is studied by the temperature-dependent current-voltage (IG–VGS) measurement. After the PMA process, the dominant gate conduction mechanism under low forward and reverse bias shifts from the trap-limited space-charge-limited conduction to generation-recombination due to the reduced hole concentration within the p-NiO layer and the improved quality of the p-NiO/AlGaN interface. Additionally, as the reverse bias increases, the trap-assisted tunneling process gradually becomes the dominant gate conduction mechanism, owing to type-II band alignment with a large band offset at the NiO/AlGaN interface and enhanced band bending in the AlGaN layer after the PMA process. Under higher forward bias, the dominant gate conduction mechanism transitions from the Poole–Frenkel emission to Ohmic conduction due to the increased gate voltage drop across the p-NiO layer with a reduced hole concentration after the PMA process. Furthermore, the proposed gate current model shows good agreement with the experimental results for both devices before and after the PMA process across a wide range of gate biases and measurement temperatures.