Effects of surface treatment for sapphire substrate on GaN films

Etch pits on sapphire substrate surface are formed after surface treating. GaN films have been grown on sapphire substrate which is treated by chemical method with different etch time by LP-MOCVD. The structure and characters of the GaN films are analyzed by high-resolution double crystal X-ray diffraction (DCXRD), three-dimension visible optics microscope (OM), scanning electron microscope (SEM) and atomic force microscope (AFM). These results indicate that the quality of GaN films grown on sapphire substrate that is chemically etched for 50 minutes is the best. High-resolution double crystal X-ray diffraction presents the GaN films grown on sapphire substrate after surface treatment for 50 minutes (0002) plane and (10-12) plane full-width at half-maximum as low as 202.68 arcsec and 300.24 acrsec, and the root mean surface (RMS) roughness is assessed and find to be 0.184 nm.