1. AIST-NU GaN Advanced Device Open Innovation Laboratory (GaN-OIL), National Institute of Advanced Industrial Science and Technology (AIST), Nagoya 464-8601, Japan
2. Electronics and Photonics Research Institute (ESPRIT), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Center 2, Tsukuba 305-8568, Japan
3. Magnetic Powder Metallurgy Research Center (MagMet), National Institute of Advanced Industrial Science and Technology (AIST), Chubu Center, Nagoya, Aichi 463-8560, Japan