Effect of Gate Edge Silicidation on Gate Leakage Current in AlGaN/GaN HEMTs

Toshihiro Ohki, Masahito Kanamura, Naoya Okamoto, Kenji Imanishi ,
Kozo Makiyama, Kazukiyo Joshin, Toshihide Kikkawa and Naoki Hara
Fujitsu Ltd. and Fujitsu Laboratories Ltd.
10-1 Morinosato-Wakamiya, Atsugi, Kanagawa, 243-0197, Japan
t-ohki@jp.fujitsu.com
Phone: +81-46-250-8242

Keywords: GaN, HEMT, power amplifier, gate leakage current

Abstract
We have demonstrated a reduction in the gate leakage current of AlGaN/GaN HEMTs by suppressing gate edge silicidation. We found that the silicidation of Ni in the gate edge during formation of the SiN passivation film caused a lower work function and increased the gate leakage current. A NiOx barrier layer inserted between the gate electrode and passivation film prevented silicidation of the gate metal and drastically reduced the gate leakage current. We also determined that silicidation was prevented by a higher oxidation rate of NiOx. The gate leakage current was attributed to both the gate edge and Schottky junction. Moreover, we confirmed no initial degradation in a DC stress test at high temperature. These results indicate that suppressing NiSi formation has a key role in reducing the gate leakage current.
 
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