Fermi-level dependent morphology in photoinduced bond breaking on (1Â 1Â 0) surfaces of III-V semiconductors

The morphology of structural changes of InP(1 1 0)-(1 × 1) and GaAs(1 1 0)-(1 × 1) induced by electronic processes following laser excitation has been studied by scanning tunneling microscopy. Surface-vacancy clusters are predominantly formed on n-type surfaces, while isolated anion monovacancies are generated almost exclusively on p-type surfaces. This remarkable Fermi-level effect in the morphology is characterized in terms of a screened Coulomb type interaction between charged surface monovacancies and carriers generated by laser excitation. It is shown that localization of photogenerated valence holes induces electronic bond rupture at surface sites.