Atomic structure and composition of the (2X4) reconstruction of InGaP(001)

In this study scanning tunneling microscopy (STM), soft x-ray photoemission spectroscopy (SXPS), and reflectance anisotropy spectroscopy were used to investigate the microscopic structure of (2x4) reconstructed TnGaP(001) sur faces. The samples were grown lattice matched on GaAs(001) by metalorganic vapor phase epitaxy. Immediately after growth the surfaces were passivated by a thick amorphous cap consisting of a P/As double layer and then transfe rred to ultrahigh vacuum (UHV) analysis chambers either equipped with STM o r connected to the BESSY synchrotron radiation source for photoemission exp eriments. Thermal desorption of the As/P capping layer at 460 degrees C und er UHV conditions lends reproducibly to the formation of a III-rich (2x4) r econstruction, the more P-rich (2x1) could not be obtained. The low energy electron diffraction image shows a clear (2x4) pattern with sharp integer-o rder and fractional-order spots. STM images show rows along the [(1) over b ar 10] direction with fourfold separation in the [110] direction, similar t o the (2x4) reconstruction of InP(001). SXPS spectra of the In 4d/Ga 3d and P 2p core levels demonstrate that this surface may consist of a mixed-dime r structure analogous to the one found on InP(001) and GaP(001) (2x4). Furt her annealing of the sample to higher temperatures degrades the surface wit hout producing another reconstruction. The (2x4) reconstruction thus repres ents the most III-rich (least P-rich) stable surface for InGaP(001), (C) 20 00 American Vacuum Society. [S0734-211X(00)05504-9].