Surface properties of the AlGaN/GaN superlattice grown at different temperatures by metalorganic chemical vapor deposition

AlGaN/GaN strained layer superlattice (SLS) structures were prepared by metalorganic vapor deposition (MOCVD) under various growth conditions. It was found that the surface morphology and V-shaped pits were determined by growth temperature. Two different types of pit were observed namely, minute pits and open V-shape pits, in scanning electronic microscopy (SEM) and atomic force microscopy (AFM) images. The density of minute pits of AlGaN/GaN SLS decreased with increasing growth temperature. It was also found that the groovelike and striplike shapes of the surface morphology of the samples prepared at 800°C revealed a preferred orientation at about 30° angle to the flat side of the substrate, but this preferred orientation was disrupted at a higher growth temperature. The samples prepared at 850 and 900°C exhibited a higher PL intensity with a peak wavelength of about 363 nm because of the improvement in the crystal quality of AlGaN/GaN SLS.