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 {1 (1) over bar 01} planes and is evidenced by the comparison of experimental diffraction patterns along [01 (1) over bar0] and [11 (2) over bar0] 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 {1 (1) over bar 01} pit facets. (C) 2003 American Institute of Physics.