Theory of Surface Dimerization-Induced Ordering in GaInP Alloys

We identify via thermodynamic energy minimization the role of subsurface strain (caused by surface reconstruction and dimerization) in the ordering of Ga0.5In0.5P alloys. Depending on the growth conditions, the alloy surfaces can have either ..beta..2(2x4), c(4x4), or c(8x6) reconstructions, with characteristic 2x1,1x2 and 2x3 RHEED patterns. We show that (i) the 1x2 reconstruction will lead to aCuPtA surface ordering, (ii) a 2x1 reconstruction will lead to a CuPtB ordering, (iii) a 2x3 reconstruction will lead to a 3-period ordering, and (iv) single (double) bilayer steps are stable at low (high) anion chemical potential. These results are in good agreement with recent experimental observations.