[1] Kyushu Univ, Grad Sch Informat Sci & Elect Engn, Dept Elect & Elect Syst Engn, Fukuoka 8128581, Japan
[2] NEC Corp Ltd, Transmiss Operat Unit, Transmiss Device Div, Dev Dept 3, Kawasaki, Kanagawa 2118666, Japan
[3] NEC Corp Ltd, Funct Mat Res Labs, Device Mat Res Lab, Kawasaki, Kanagawa 2168555, Japan