Step structure on the GaAs(2 5 11) surface

Abstract: GaAs samples off-oriented from (2 5 11) by 1degrees and 5.2degrees were prepared by molecular-beam epitaxy and characterised in situ by scanning tunneling microscopy. Terraces of the GaAs(2 5 11) surface are separated by steps along three characteristic directions [3 1 (1) over bar], [4 5 (3) over bar], and [2 (3) over bar 1] which are equivalent to the intersections of the (0 1 1) (I I 3)A. and (I I I)A planes with the (2 5 11) plane, respectively. On the basis of atomically resolved step images, step models were developed and analyzed with help of the electron counting rule (ECR). Step bunches along [3 1 (1) over bar] form (0 1 1) facets. According to the derived models the steps along [3 1 (1) over bar] fulfill the ECR. whereas the steps along [4 5 (3) over bar] violate it. Steps along [2 (3) over bar 1] violate the ECR as well. but may fulfill it over mesoscopic areas