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

Scanning tunneling microscopy (STM) was used to investigate the microscopic structure of the phosphorous (P)-rich so-called (2 x 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 x 1)/(2 x 2) periodicity with streaks in the [110] direction. STM images display rows in the [110] direction formed by randomly distributed (2 x 2)/(2 x 2 )lc(4 x 2)-like local structures plus many defects. This disorder effect explains the (2 x 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 degrees 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 x 2) or c(4 x 2) reconstructions. The structure of the rows can be explained in terms of buckled P dimers oriented along the [110] direction on a complete In layer. [S0163-1829(99)51532-4].