The donor Te has been added to GaInP during organometallic vapor phase epitaxial growth using the precursor diethyltelluride. In agreement with previous studies, the addition of high Te concentrations leads to the elimination of the CuPt ordering observed in undoped layers. The degree of order is estimated from the low temperature photoluminescence peak energy to decrease from 0.5 at Te concentrations of Ͻ2ϫ10 17 cm Ϫ3 to 0 for Te concentrations of Ͼ6ϫ10 17 cm Ϫ3 . This is verified by transmission electron diffraction studies, which show the elimination of the 1/2͕111͖ superlattice spots at high Te doping levels. A remarkable change in the surface structure is found to accompany this decrease in ordering: The surfaces become much smoother.Step bunching is observed to disappear for the vicinal GaAs substrates, misoriented from ͑001͒ by 3°in the B direction, and three-dimensional island ͑or mound͒ formation is eliminated for the singular ͑001͒ substrates. A qualitative model is presented explaining this behavior based on the effect of Te on the step structure and the bonding at step edges, both of which affect the adatom sticking at steps.

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Transmission electron microscope (TEM) and transmission electron diffraction studies have been performed to investigate the effects of Te doping on ordering and antiphase boundaries (APBs) in organometallic vapour phase epitaxial Ga 0.5 In 0.5 P layers grown on (001) GaAs singular and vicinal substrates at 670 • C. TEM results show that the behaviour of APBs for the singular samples differs from that of the vicinal samples. The density of APBs in the vicinal samples is increased by roughly a factor of 2, whilst that of the singular samples is slightly increased, as the Te concentration increases. APBs are inclined 10-57 • from the (001) growth surface. As for the singular samples, the angle seems to remain virtually unchanged with increasing doping level. However, for the vicinal samples, the angle decreases significantly with increasing concentration. A simple model is presented to explain the dopant concentration dependence of the behaviour of APBs in the ordered GaInP.