Ordering Effect On Band-Gap Lowering In Lattice-Matched Inalas Epilayers Grown On Inp By Metal-Organic Chemical-Vapor Deposition

Band-gap lowering due only to the cation ordering effect is investigated in InAlAs layers grown on InP by using photoluminescence measurement. Double-crystal x-ray diffraction and Rutherford backscattering measurements confirm that both of the InAlAs epilayers studied, grown at 700 and 750 degrees C, are lattice matched with InP substrates. Through transmission electron diffraction measurements, it is observed that a CuPt-type ordering structure is formed in the InAlAs layers grown at 700 degrees C but not in the layers at 750 degrees C. Photoluminescence measurements at 1.7 K reveal that the band-gap energy of the ordered InAlAs is smaller by 60 meV than that of the unordered InAlAs. (C) 1998 American Institute of Physics.