Optimized Pre-Treatment Process for MOS-GaN Devices Passivation

In this letter, we present an effective GaN surface passivation process, which was developed by optimizing the surface chemical pretreatment prior to the PECVD- SiO_x deposition. It is demonstrated that the electronic properties of the GaN/SiO_x interface are drastically influenced by the surface preparation conditions. Among the used chemicals, we found that KOH/HCl leads to the best GaN/SiO_x interface quality. MOS capacitors fabricated using this pretreatment have shown a near ideal capacitance-voltage characteristics, with a good surface potential modulation, small flatband voltage shift, low hysteresis, and no significant frequency dispersion. Using this optimized passivation process, AlGaN/GaN-based MOS-high electron mobility transistors (HEMTs) were fabricated. Electrical characterizations have shown up to four orders of magnitude lower gate leakage current and three orders of magnitude lower off-state current compared with the reference Schottky gate HEMT.