Photoelectrochemical Properties of Single Crystalline and Polycrystalline GaN Grown by the Na-flux Method

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A single crystal and polycrystals of GaN grown by the Na-flux method were photoelectrochemically characterized. The flatband potential of the GaN single crystal was approximately 0.2 V anodic of the potential of the GaN layer grown by metal-organic vapor phase epitaxy. Clear photo-electrochemical response was observed for the GaN single crystal. The turn-on slopes of the photocurrent for the poly-crystalline samples were gentler than the slope for the single crystal. The turn-on slopes were probably affected by the high resistivity of grain boundaries in the polycrystalline samples.