Evidence for a Surface-State Exciton on GaAs(110)

Abstract

Synchrotron-radiation photoemission data are obtained from GaAs ($\overline{1}\overline{1}0$) and (110) faces for $s$ and $p$ polarization which show an enhancement of valence-electron emission for initial states at and below the valence-band maximum when the photon energy is scanned through the threshold for Ga-$3d$-core to intrinsic-surface-state excitations. The enhancement is interpreted as a core surface exciton associated with the Ga dangling bonds.