Improvement of Current Collapse by Surface Treatment and Passivation Layer in p-GaN Gate GaN High-Electron-Mobility Transistors

The improvement of current collapses of p-GaN gate GaN high-electron-mobility transistors (HEMTs) caused by the effects of surface treatment and the passivation layer was investigated. The NH3 treatment and high-temperature oxide (HTO) passivation layer on the AlGaN layer are effective in improving the current collapse of a p-GaN gate GaN HEMT. The current collapse at a long time constant (τ= 4 s) could be decreased by the NH3 treatment of the AlGaN layer, because the nitrogen atoms in nitrogen vacancies in the AlGaN layer (trap level: 0.6 eV) would be incorporated, resulting in a low surface density. The current collapse at an intermediate time constant (τ= 11 ms) could also be decreased by the deposition of the HTO passivation layer on the AlGaN layer, because the low-interface-density layer (trap level: 0.4 eV) of HTO/AlGaN would be formed.