A Ga oxide layer was successfully grown on a n-GaN substrate by using a bias, UV-assisted technique in deionized (DI) water at room temperature. An Al electrode, instead of a Pt electrode, was used as the counter electrode to apply a negative bias to the DI water. The thickness of the grown oxide layer strongly depended on the intensity of the UV radiation illuminating the substrate and on the positive bias applied to the substrate. UV illumination contributed to electron-hole pair generation.

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... ncreasing the positive bias deepened the potential well so that more minority carriers were confined in the potential well and accumulated on the surface. Thus, increasing the UV intensity and the applied bias increased the thickness of the grown Ga oxide. However, the oxide growth rate decreased with time, and the oxide layer thickness saturated to 330 nm at 15 V and 160 nm at 5 V under an UV illumination of 300 mW/cm 2 . The auger electron spectroscopy analysis of the grown oxide layer showed uniform growth with oxygen and gallium atomic percents of about 36 % and 58 %, which is close to the stoichiometric composition of Ga2O3.