Step Structures on III-V Phosphide (001) Surfaces: How Do Steps and Sb Affect CuPt Ordering of GaInP2?

The observation of III-V phosphide (001)-(2 × 2) surfaces makes it possible to solve a long standing mystery of step structures. First-principles calculations show that a bulklike type-B step on a hydrogenated 2 × 2 surface is more stable than a rebonded one by 1.1 eV/unit step. In contrast, this energy difference for a H-free β(2 × 4) surface is only 0.5 eV/unit step. The large difference explains why the CuPt ordering of GaInP is stronger in metal-organic chemical vapor deposition than in molecular beam epitaxy. However, a minute amount of Sb will preferentially attach to the 2 × 2 surface steps and induce additional step structures that cause ordering disruption.