GaAs1minus;xPxwith 0.4le;xle;0.85 forms the CuPt ordered structure during organometallic vapor phase epitaxy (OMVPE). Only the (1macr;11) and (11macr;1) variants are observed for growth on (001)hyphen;oriented substrates. The mechanism by which ordering occurs is only now being discovered. Total energy calculations, including the effects of surface reconstruction, indicate that the phenomenon can be explained purely on the basis of energy considerations. Indirect evidence indicates that kinetic factors, including processes occurring at steps propagating across the surface in the twohyphen;dimensional growth mode, control ordering. In this work, GaAs1minus;xPxlayers have been grown by OMVPE on (001)hyphen;oriented GaAs0.6P0.4lsquo;lsquo;substrates.rsquo;rsquo; In order to examine the effects of surface kinetic factors, the substrates were first patterned with lsqb;110rsqb;hyphen;oriented grooves 5 mgr;m wide and a fraction of a micron deep. The groove is used to provide a source of steps moving in opposite directions from the two edges. Transmission electron diffraction reveals the formation of large domains of the two variants that meet in the center of the groove. A surprising feature is the presence of a region in the groove with absolutely no ordering. Tracing the surface shape during growth using a superlattice structure indicates that the disordered region is due to growth on lcub;511rcub; facets. The domains formed after the groove is filled are very large, several square microns in crosshyphen;sectional area and extending along the entire length of the groove. These results demonstrate that natural ordering in GaAsP, an alloy with mixing on the group V sublattice, can be controlled by regulating the propagation of steps during growth, exactly as for GaInP where mixing is on the group III sublattice.
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