“…Judging from the energy bandgap and conduction band offset between the insulators and the GaN-related materials, alumina (Al 2 O 3 ), SiO 2 , and their nitrides seem to be possible candidates for gate dielectrics. [1][2][3][4][5][6][7][8][9][10][11][12][13][14] Since the atomic layer deposition (ALD) technique for producing high-quality Al 2 O 3 was established, ALD-Al 2 O 3 films have been widely used for GaN-based MOS devices. 4,6,7,[10][11][12] However, regardless of the film deposition technique used, Al 2 O 3 involves an essential problem of electron trapping, 6,13,14) thus leading to significant I d -V g hysteresis and V th instability (positive V th shift).…”