XRD, AFM and IR investigations of ordered AlGaAs2 phase in epitaxial AlxGa1-xAs/GaAs (100) heterostructures

The lattice constant of AlxGa1−xAs epitaxial alloys with various Al‐As(x) content is determined for AlxGa1−xAs/GaAs (100) heterostructures grown by MOVPE epitaxy using X‐ray diffractometry and X‐ray back‐reflections method. An ordered AlGaAs2 (superstructural) phase was found in epitaxial heterostructures for x ∼ 0.50. The lattice constant of this phase along c axis is smaller than the double lattice constants of an Al0.50Ga0.50As alloy. Infrared (IR) reflection spectra of lattice vibrations were investigated in epitaxial heterostructures of AlxGa1−xAs/GaAs (100) with different concentrations of Al in cation sublattice. In the sample with x ∼ 0.50, besides two main vibration modes some additional ones were found that correspond to superstructure ordered phase AlGaAs2. Atomic‐force microscopy (AFM) of the sample surface with x ∼ 0.50 demonstrated the presence of areas with ordered nano‐relief having period of ∼115 nm that can be related with superstructure phase of AlGaAs2. Copyright © 2006 John Wiley & Sons, Ltd.