Investigation into water-induced surface oxidization of GaN lamella structure

The interaction between gallium nitride (GaN) and H₂O has been thoroughly investigated using a novel methodology involving the fabrication of a well-defined nanometer scale GaN lamella by means of a focused ion beam milling technique. Electrical characterization results show that the exposure of the GaN surface to water at room temperature causes the device resistivity to continuously increase, which makes the GaN lamella a stable polar liquid sensor. To explain the relationship between the reduced conductivity of GaN and water dissociation on the GaN surface, we utilize surface sensitive x-ray photoelectron spectroscopy and density-functional theory calculations to investigate surface oxidation of the dry and wet GaN surface. Our studies show that the water molecules are stably adsorbed on the GaN surface and are favorable to being dissociated into hydrogen atoms and hydroxyl groups on the GaN surface even if the surface is oxidized. (paper)