1：Experimental Design and Method Selection:

The study involved fabricating Pt-gated Al2O3/n-GaN MOS capacitors with native oxide interlayers, using atomic layer deposition (ALD) for Al2O3 films and post-metallization annealing (PMA) to improve interface properties. Capacitance-voltage (C-V) and current-voltage (I-V) measurements were conducted to analyze electrical characteristics.

2：Sample Selection and Data Sources:

Samples were prepared using Si-doped GaN epilayers on freestanding n+-GaN(0001) substrates. Two types of capacitors were made: one with a native oxide interlayer (cleaned with SPM only) and one with a reduced native oxide interlayer (cleaned with SPM and BHF).

3：List of Experimental Equipment and Materials:

Equipment included ALD system for Al2O3 deposition, Agilent B1500A semiconductor device parameter analyzer for C-V measurements, Keithley 4200-SCS for I-V measurements, X-ray photoemission spectroscopy (XPS) for surface analysis, and spectroscopic ellipsometry for thickness measurement. Materials included sulfuric acid peroxide mixture (SPM), buffered hydrofluoric acid (BHF), trimethylaluminum (TMA) precursor, H2O oxidant gas, Pt and Ti for electrodes.

4：Experimental Procedures and Operational Workflow:

GaN surfaces were cleaned with SPM or SPM+BHF. Al2O3 films (10-30 nm thick) were deposited via ALD at 300°C using TMA and H2O. Pt gate electrodes and ohmic contacts were deposited. PMA was performed at 300-600°C under N2 atmosphere. C-V and I-V measurements were done at room temperature in dark conditions.

5：2O. Pt gate electrodes and ohmic contacts were deposited. PMA was performed at 300-600°C under N2 atmosphere. C-V and I-V measurements were done at room temperature in dark conditions. Data Analysis Methods:

5. Data Analysis Methods: Vfb and CET were estimated from C-V data using MIRAI-ACCEPT software. Interface state density (Dit) was determined using a conductance method. XPS was used to analyze the native oxide layer.