Step Structures on Vicinal InAs (001) under ( 2×4) and ( 4×2) Surface Reconstructions

Step structures on InAs (001) vicinal surfaces under two different surface reconstructions were investigated by scanning tunneling microscopy. On an InAs surface misoriented by 1° toward the [110] direction, relatively straight monolayer steps along the [11̄0] direction were observed under an As-stabilized (2×4) reconstruction. On the other hand, step-bunching of about 10 monolayers was detected under an In-stabilized (4×2) reconstruction. On an InAs surface misoriented by 1° toward the [11̄0] direction, ragged monolayer steps roughly running parallel to the [110] direction were seen under the (2×4) reconstruction. However, relatively straight steps along the [110] direction with step-bunching of 2-3 monolayers were observed under the (4×2) reconstruction. These results indicate that thermodynamically favorable step structures are different between the (2×4) and (4×2) reconstructions.