Suppression of Current Collapse of High-Voltage AlGaN/GaN HFETs on Si Substrates by Utilizing a Graded Field-Plate Structure. - Tadayoshi Deguchi; Hideshi Tomita; Atsushi Kamada; Manabu Arai; Kimiyoshi Yamasaki; Takashi Egawa (IEICE Trans. Electron., 2012)