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Al 2 O 3 deposited by atomic layer deposition (ALD) was focused 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 an X-ray photoelectron spectroscopy (XPS). 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 indicate that the fixed charge in the Al 2 O 3 layer is decreased by 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 the good DC I-V characteristics with the forward bias over 6 V, and the drain leakage current in the off-state region was suppressed by seven orders of magnitude.

Graphene layers were synthesized by annealing amorphous carbon (a-C) thin films on Ni/SiO 2 / Si(111) substrates grown using pulse arc plasma deposition. Although the graphene layers were formed by catalytic reaction between a-C films and Ni metals, they were observed to be directly on the insulating SiO 2 /Si substrates with island-shaped metallic particles. These particles presumably resulted from agglomeration phenomena of thin Ni films at a high temperature. We speculated that the agglomeration phenomena allowed the graphene formation on SiO 2 /Si substrates. It was also confirmed that the particle size and graphene layer thickness depend on the starting Ni thickness. V

Frequency dependent conductance measurements were employed to study the trapping effects of in-situ metal-organic chemical vapor deposition grown AlN/AlGaN/GaN metal-insulator-semiconductor heterostructures (MISHs). Conventional fitting method could not be used to explain the experimental parallel conductance (Gp/ω ) results. Alternatively, experimental Gp/ω values were resolved into two fitting curves for gate voltages (−1.2 to −1.8 V) near the threshold voltage (Vth) by a fitting model. In the low frequency region (≤50 kHz), the Gp/ω values can be fitted into a single curve. On the other hand, in the high frequency region, two fitting curves were necessary. The results using this model explicitly yielded two types of traps existing in the AlN/AlGaN/GaN MISHs, one due to the insulating AlN layer and the other caused by the AlGaN barrier layer.

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