CuPt-Ordering in High Bandgap GaxIn1-xP Alloys on Relaxed GaAsP Step Grades

We have fabricated a series of Ga_x In_1-x P samples over the compositional range 0.51<x<0.76 on GaAs substrates. The samples were prepared by first growing a thick step-graded layer of GaAs1-y P ^y to bridge the lattice misfit between the Ga_x In _1-x P layers and the GaAs substrate. The order parameter was tuned using a dilute antimony surfactant during growth. The composition, strain, and order parameter of each sample were characterized by x-ray diffraction, and the bandgap was measured by photoluminescence. We find good agreement between the experimentally measured bandgaps and theoretically modeled curves.