Unoccupied surface states on GaP(111) surfaces

摘要

Unoccupied surface electronic states have been observed on GaP(111) surfaces by momentum-resolved inverse photoemission spectroscopy (IPES). On the GaP($OBAR@111):P surface an unoccupied state is detected 1.2 eV above the Fermi level. This state is associated with Ga surface adatoms, since prolonged exposure to the incident electron beam removes this IPES feature and reduces the Ga/P ratio in Auger electron spectrum. Preferential photon absorption at 2.27 eV by this surface can be explained by promotion of an electron from the valence band maximum to the unoccupied surface state detected in this work.