Pyramidal-plane ordering in AlGaN alloys

This letter reports the identification of long-range ordering in AlGaN compounds along the pyramidal planes by transmission electron microscopy. This ordering consists of the alternate stacking of GaN and AlN layers on {1101} planes and is evidenced by the comparison of experimental diffraction patterns along [0110] and [1120] with calculated patterns. A formation model of this ordering is presented. It is based upon Ga incorporation on reduced-N coordination sites that are located at step edges on {1101} pit facets.