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 investigat ed in InAlAs layers grown on InP by using photoluminescence measuremen t. Double-crystal x-ray diffraction and Rutherford backscattering meas urements confirm that both of the InAlAs epilayers studied, grown at 7 00 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. Photoluminescenc e 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) 19 98 American Institute of Physics.