Achievement of normally-off AlGaN/GaN high-electron mobility transistor with p-NiO x capping layer by sputtering and post-annealing

Shyh Jer Huang, Cheng Wei Chou*, Yan Kuin Su, Jyun Hao Lin, Hsin-Chieh Yu, De Long Chen, Jian Long Ruan

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


In this paper, we present a technique to fabricate normally off GaN-based high-electron mobility transistor (HEMT) by sputtering and post-annealing p-NiO x capping layer. The p-NiO x layer is produced by sputtering at room temperature and post-annealing at 500 °C for 30 min in pure O 2 environment to achieve high hole concentration. The V th shifts from −3 V in the conventional transistor to 0.33 V, and on/off current ratio became 10 7 . The forward and reverse gate breakdown increase from 3.5 V and −78 V to 10 V and −198 V, respectively. The reverse gate leakage current is 10 −9 A/mm, and the off-state drain-leakage current is 10 −8 A/mm. The V th hysteresis is extremely small at about 33 mV. We also investigate the mechanism that increases hole concentration of p-NiO x after annealing in oxygen environment resulted from the change of Ni 2+ to Ni 3+ and the surge of (111)-orientation.

Original languageEnglish
Pages (from-to)373-377
Number of pages5
JournalApplied Surface Science
StatePublished - 15 Apr 2017


  • Enhancement mode
  • Gallium nitride
  • HEMTs
  • Sputter
  • p-NiO

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