We infer the structure of the $\mathrm{GaP}\mathrm{}\left(001\right)(2\mathrm{}\times 4)$ surface from a study of scanning tunneling microscopy (STM) images obtained under UHV conditions on metal-organic vapor phase epitaxy grown samples. STM images are compared with results of first-principles calculations for models energetically most favorable under Ga-rich growth conditions. The comparison shows that the $\mathrm{GaP}\mathrm{}\left(001\right)(2\mathrm{}\times 4)$ surface unit cell consists of a mixed Ga-P dimer on top of a complete gallium layer, hence ruling out the Ga-Ga dimer model.

• Received 18 April 2000

DOI:https://doi.org/10.1103/PhysRevB.62.11046