Resonant Photoemission from Al-GaAs(110) Interfaces

Resonant enhancement of photoemission cross sections for valence bands of Al-GaAs(110) surfaces has been observed in the vicinity of the Al $2p$ core-excitation threshold. The observation provides strong evidence for the existence of an Al $2p$ extrinsic surface core exciton which decays into single and double final hole states, resulting in two types of resonance. Features of these resonances are found to be drastically changed with Al coverage.