Electrical properties of GaN-based metal–insulator–semiconductor structures with Al2O3deposited by atomic layer deposition using water and ozone as the oxygen precursors

Al 2 O 3 deposited by atomic layer deposition (ALD) was used as an insulator in metal–insulator–semiconductor (MIS) structures for GaN-based MIS-devices. As the oxygen precursors for the ALD process, water (H 2 O), ozone (O 3 ), and both H 2 O and O 3 were used. The chemical characteristics of the ALD-Al 2 O 3 surfaces were investigated by x-ray photoelectron spectroscopy. After fabrication of MIS-diodes and MIS-high-electron-mobility transistors (MIS-HEMTs) with the ALD-Al 2 O 3 , their electrical properties were evaluated by current–voltage ( I – V ) and capacitance–voltage ( C – V ) measurements. The threshold voltage of the C – V curves for MIS-diodes indicated that the fixed charge in the Al 2 O 3 layer is decreased when using both H 2 O and O 3 as the oxygen precursors. Furthermore, MIS-HEMTs with the H 2 O + O 3 -based Al 2 O 3 showed good dc I – V characteristics without post-deposition annealing of the ALD-Al 2 O 3 , and the drain leakage current in the off-state region was suppressed by seven orders of magnitude.