Observations of segregation of Al in AlGaN alloys

Transmission electron microscopy has been used to characterize Al segregation in Al 0.1 Ga 0.9 N and Al 0.3 Ga 0.7 N alloys grown by metal organic chemical vapor deposition on 6H-SiC. It has been found that an interlayer of AlGaN alloy with much higher Al content was formed at first, followed by normal growth of nominal composition of AlGaN alloy. In Al 0.1 Ga 0.9 N and Al 0.3 Ga 0.7 N films, dislocation lines were also found to have more Al segregated than those regions free of dislocations in the matrix. Furthermore, it shows that more Al atoms segregate to an edge dislocation than to a screw one.