Effects of Substrate Orientation on the Spontaneous Ordering of GaAsSb Epilayers Grown by Molecular Beam Epitaxy

摘要

Spontaneous atomic ordering is investigated in a series of GaAs_(1-x)Sb_x epilayers (0.51 < x < 0.71) grown by molecular beam epitaxy (MBE) on GaAs substrates with surface orientations of (001), (001) - 8~0 toward (111)A, (001) - 8~0 toward (111)B, (115)A, (115)B, (113)A, and (113)B. Atomic ordering in these epilayers was observed from a decrease in the energy gap measured by Fourier transform infrared (FTIR) absorption spectroscopy and corroborated by superlattice reflections in transmission electron diffraction and Raman spectroscopy. Contrary to previous investigations of ordering in Ⅲ-Ⅴ alloys, a marked energy gap reduction corresponding to CuPt-B type ordering is observed in the GaAs_(1-x)Sb_x grown on (111)A-type orientations.