Gate technology contributions to collapse of drain current in AlGaN/GaN schottky HEMT

Takamasa Kawanago, Kuniyuki Kakushima, Yoshinori Kataoka, Akira Nishiyama, Nobuyuki Sugii, Hitoshi Wakabayashi, Kazuo Tsutsui, Kenji Natori, Hiroshi Iwai

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13 Scopus citations


Contributions of gate metal to electrical characteristics in AlGaN/GaN Schottky HEMT are reported. The focus is on the collapse of drain current associated with Schottky metals. Ni and W gate introduce electrically active defects under the gate metal in AlGaN layer. These electrically active defects induce the current collapse, higher gate leakage current, and frequency dispersion in C{-}V characteristics. Contrarily, TiN metal seems to mitigate the appearance of such electrically active defects. The observed current collapse is not the permanent but the recoverable degradation by means of light exposure irrespectively of the gate metals, suggesting the involvement of electron trapping on defects, particularly at the gate edge on the drain side where the electric field is the highest. The nitrogen vacancies in the AlGaN layer underneath the Schottky gate are plausible origin that is responsible for the electrically active defects based on the dependence of nitrogen concentration in TiN metal on the current collapse, which can be explained in terms of nitrogen diffusion from the AlGaN layer to the gate metal.

Original languageEnglish
Article number6732947
Pages (from-to)785-792
Number of pages8
JournalIEEE Transactions on Electron Devices
Issue number3
StatePublished - Mar 2014


  • AlGaN/GaN high electron mobility transistor (HEMT)
  • current collapse
  • nitrogen vacancies
  • Schottky gate
  • TiN gate

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