COMPARATIVE-STUDY OF ATOMIC ORDERING AND ALLOY CLUSTERING IN INGAP CRYSTALS GROWN BY METALORGANIC VAPOR-PHASE EPITAXY, CHLORIDE-VAPOR PHASE EPITAXY, AND LIQUID-PHASE EPITAXY

We describe the results of the transmission electron microscope study of ordered and modulated structures in InGaP alloy semiconductors grown on (001) GaAs substrates by metalorganic vapor phase epitaxy, chloride-vapor phase epitaxy, and liquid phase epitaxy. Strong ordering of CuPt-type has been observed in InGaP grown by metalorganic vapor phase epitaxy at 630 °C, which is associated with an abnormality in the photoluminescence peak energy. CuPt-type ordered structures have also been observed in crystals grown by chloride-vapor phase epitaxy, but the degree of ordering is weaker and crystals grown at 576-740 °C exhibit normal photoluminescence peak energies. On the other hand, in crystals grown by liquid phase epitaxy, no ordered structure is found and the crystals exhibit normal photoluminescence peak energies. There is no dependence of modulated structures on the growth method since they are observed in all crystals. These results also lead us the previous conclusion by Kondow and co-workers that the ordered structures are not generated under thermal equilibrium conditions but rather by the diffusion and reconstruction of deposited atoms on the growth surface.