A novel process has been developed to grow GaN films and GaN-based light emitting diodes on the sapphire substrates with high-density nano-craters formed on the surface of the substartes in situ metalorganic vapor phase epitaxial (MOCVD) reactor. The whole process is a single and integrated MOCVD run. Firstly a thin GaN layer is grown on the sapphire substrate, and then it is etched away by only flowing the H2 into the reactor at the higher temperature. It is found, amazingly, that the thermal decomposition of GaN can induce the chemical etching of sapphire, and result in the formation of high-density nano-craters on the surface of the substrates. Finally the device-quality GaN films could be grown on the etched sapphire substrate with the residual gallium droplets as nucleation sites. A preliminary result shows that the output power of GaN light-emitting diodes built on the in situ etched sapphire substrates could be increased by 30%.
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