Atomic surface structure of the phosphorous-terminated InP(001) grown by MOVPE

Abstract

Scanning tunneling microscopy (STM) was used to investigate the microscopic structure of the phosphorous (P)-rich so-called $(2\ifmmode\times\else\texttimes\fi{}1)$ reconstruction of InP(001). The samples were homoepitaxially grown in a commercial metal-organic vapor phase epitaxy reactor and then transferred under ultra high vacuum (UHV) conditions into a separate UHV- chamber equipped with low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM). After transfer LEED patterns show a $(2\ifmmode\times\else\texttimes\fi{}1)/(2\ifmmode\times\else\texttimes\fi{}2)$ periodicity with streaks in the $[1\ifmmode\bar\else\textasciimacron\fi{}10]$ direction. STM images display rows in the [110] direction formed by randomly distributed $(2\ifmmode\times\else\texttimes\fi{}2)/c(2\ifmmode\times\else\texttimes\fi{}2)/c(4\ifmmode\times\else\texttimes\fi{}2)$-like local structures plus many defects. This disorder effect explains the $(2\ifmmode\times\else\texttimes\fi{}1)$-like LEED pattern. The structure of the rows is interpreted in terms of P dimers directed along the [110] direction which are adsorbed on a complete P layer underneath. Prolonged annealing at $350\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ causes successive desorption of single P dimers as monitored by STM. The LEED pattern remains essentially unaffected and STM images with atomic resolution reveal zig-zag chains in the [110] direction separated by twice the lattice constant. Two adjacent rows can be in or out of phase thus resulting in either $p(2\ifmmode\times\else\texttimes\fi{}2)$ or $c(4\ifmmode\times\else\texttimes\fi{}2)$ reconstructions. The structure of the rows can be explained in terms of buckled P dimers oriented along the $[1\ifmmode\bar\else\textasciimacron\fi{}10]$ direction on a complete In layer.