CuPt-B type spontaneous atomic ordering has been investigated in AlInP epilayers grown by organometallic vapor phase epitaxy (MOVPE) with different input flux Will ratios. Transmission electron diffraction (TED) patterns and transmission electron microscopy (TEM) images of the sample confirm the CuPt-B type ordering in the MOVPE-grown AlInP epilayers. At the growth temperature of 630 degrees C, the ordering degree of the AlInP epilayer has been found to change with the input flux V/III ratio of the MOVPE growth. The degree of atomic ordering decreases when the input V/III ratio of the MOVPE growth is reduced from 60 to 20. The AlInP epilayer grown with the lower input V/III ratio has a lower ordering degree because of the reduction of the P-P dimer concentration formed on the growing surface during the MOVPE growth. The ordering degree of the AlInP epilayer also decreases when the input V/III ratio in the MOVPE growth increases above 60. This result is attributed to a reduction of the diffusion length of the group III adatoms with the higher Will ratio during MOVPE growth. (C) 2010 Elsevier B.V. All rights reserved.