An unusually large Schottky barrier (≳1.1 eV) is demonstrated by studies of Au on atomically cleann‐type GaAs. It is suggested that this large barrier is produced by Au moving beneath the surface and introducing new gap states close to the valence band maximum. These new gap states can overcome the defect states (produced during the adsorption process) that normally pin the Fermi energy near midgap, thus increasing the barrier height. Starting with an atomically clean surface appears essential.