Comparison of Ordered and Modulated Structures in InGaP Alloy Semiconductors grown by MOCVD, Chloride-Vpe and LPE Methods

Abstract

AbstractOrdered and modulated structures in InGaP alloy semiconductors grown on (001) GaAs substrates by metalorganic chemical vapor deposition, chloride-vapor phase epitaxy, and liquid phase epitaxy have been systematically studied by transmission electron microscopy. In InGaP grown by metalorganic chemical vapor deposition at 630°C, strong ordering of CuPt-type has been observed, which is associated with an abnormality in the photoluminescence peak energy. For crystals grown by chloride-vapor phase epitaxy, CuPt-type ordered structures have also been observed. However, the degree of ordering is weaker in the latter case and crystals grown at 576-740°C exhibit normal photoluminescence peak energies. On the other hand, in crystals grown by liquid phase epitaxy, no superstructure spots are found in the electron diffraction patterns and the crystals exhibit normal photoluminescence peak energies. Modulated structures do not depend on the growth method since they are observed in all crystals. From these results, it has been concluded 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.