Remarkable Current Collapse Suppression in GaN HEMTs on Free-standing GaN Substrates. - Yusuke Kumazaki; Keiji Watanabe; Toshihiro Ohki; Junji Kotani; Shiro Ozaki; Yoshitaka Niida; Kozo Makiyama; Yuichi Minoura; Naoya Okamoto; Norikazu Nakamura (BCICTS, 2019)