SURFACE DIMERIZATION INDUCED CUPTB VERSUS CUPTA ORDERING OF GAINP ALLOYS

Using a valence force field approach and ab initio pseudopotential cal culations, we examine the role of subsurface strain in the ordering of Ga0.5In0.5P alloys. We show that depending on the orientation of the surface phosphorus dimers, these alloys can have (i) a CuPtA ordering for 1X2 or c(4X4) reconstruction; (ii) a CuPtB ordering for 2X1 or bet a 2(2X4) reconstruction; and (iii) a triple period ordering for 2X3 or c(8X6) reconstruction. These results are in good agreement with recen t experiments of Gomyo et al. [Phys. Rev. Lett. 72, 673 (1994); Jpn. J . Appl. Phys. 34, L469 (1995)]. (C) 1995 American Institute of Physics .