Reconstruction and chemical ordering at the surface of strained (In, Ga) As epilayers

An evidence for a cation chemical ordering in 2 × 3 reconstructed surfaces of strained InxGa1−xAs layers, locking the composition at the value In0.67Ga0.33As, has been obtained by grazing incidence X-ray diffraction. For lower surface concentrations, the reconstruction becomes incommensurate 2 × n and is described by introducing a random distribution of indium-free faults in the commensurate 2 × 3 phase. A quantitative account of the intensity distribution is obtained.