Gallium nitride (GaN) films were grown on sapphire and zinc oxide (ZnO) single crystal substrates using plasma-assisted molecular beam epitaxy. As ZnO for GaN have a better lattice match, the coverage ratio of the GaN (002) plane on the ZnO substrate was significantly higher by about 45%. According to conducting atomic force microscopy and scanning surface potential microscopy measurements, the surface of GaN films grown on the ZnO substrate had two excellent physical characteristics: (a) an 18% reduction of the high contact current region, and (b) a highly uniform work function distribution. Therefore, for future applications in GaN-based light-emitting diodes, the use of ZnO as a substrate will prolong the luminescence lifetime and enhance the luminescent monochromaticity.
Keywords: conducting atomic force microscopy; gallium nitride; scanning surface potential microscopy; zinc oxide.
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