MOVPE Growth of GaN Thin Films on A Misoriented Sapphire Substrate

The effects of slight misorientation from a singular plane on sapphire (α-Al2O3) substrates on the surface morphology and luminescence properties of MOVPE-grown GaN films have been studied. Macrostep morphology with periodic terraces (singular plane) and risers (clustered steps) has been observed for the first time on epitaxial GaN films grown on 3°–10° misoriented sapphire substrates toward both the View the MathML sourcesapphire and View the MathML sourcesapphire directions. In addition, it is found that the macrostep causes inhomogeneity of cathodoluminescence (CL) and electroluminescence (EL) patterns in Zn-doped GaN films, suggesting that the Zn-luminescence center formation depends on the growth planes of the terrace and riser.

A novel metalorganic chemical vapor deposition (MOCVD) system, which has two different flows, has been developed. One flow carries a reactant gas parallel to the substrate, and the other an inactive gas perpendicular to the substrate for the purpose of changing the direction of the reactant gas flow. The growth of a GaN film was attempted using this system, and a high quality, uniform film was obtained over a  in sapphire substrate. The carrier concentration and Hall mobility are 1×1018/cm3 and 200 cm2/V s, respectively, which are the highest for GaN films grown directly on a sapphire substrate by the MOCVD method.


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