Surface structure of ordered InGaP(001): The(2×4)reconstruction

Abstract

In this study the atomic structure of $(2\ifmmode\times\else\texttimes\fi{}4)$ reconstructed ${\mathrm{In}}_{0.48}{\mathrm{Ga}}_{0.52}\mathrm{P}(001)$ surfaces is analyzed by scanning tunneling microscopy (STM) and soft x-ray photoemission spectroscopy (SXPS). The samples were grown lattice matched on GaAs(001) by metal organic vapor phase epitaxy. Immediately after growth the surfaces were passivated by a P/As-double-layer cap and then transferred to ultrahigh vacuum (UHV) analysis chambers for surface characterization. Under UHV conditions an uncontaminated, well ordered $(2\ifmmode\times\else\texttimes\fi{}4)$ reconstruction was reproducibly formed by thermal annealing for $10\mathrm{min}$ at $460{}^{\ifmmode^\circ\else\textdegree\fi{}}\mathrm{C}.$ STM images with atomic resolution were obtained showing features typical for the mixed-dimer $(2\ifmmode\times\else\texttimes\fi{}4)$ structure as known from InP(001). This interpretation is substantiated by the appearance of two surface core level components in the SXPS spectra of In $4d$ and $\mathrm{Ga}3d$ plus one in the $\mathrm{P}2p$ emission line, as expected for the mixed-dimer structure. Further annealing of the sample to higher temperatures under UHV degrades the surface without producing any other reconstruction. The $(2\ifmmode\times\else\texttimes\fi{}4)$ mixed dimer structure thus represents the most III-rich (least P-rich) stable (001) surface.