Atomic geometry and electronic states on GaAs(1 1 1)A–Se(23×23)

In this work we have performed a theoretical study of the atomic geometry and scanning tunelling microscopy simulation of the GaAs(1 1 1)A–Se(23×23) surface. The calculated geometry with Se trimers on H3 sites agrees well with results reported recently from STM and RHEED experiments. Simulated STM images, corresponding to orbital localisation near the fundamental gap, support the experimental observations of bright spots on Se trimers.