We present experimental results from infrared photocurrent measurements at the Si/metal andSi/SiO2/metalinterface. We observe internal photoemission from the Si valence band into metal states or into empty interface states. For thep-Si/SiO2/metalinterface the photocurrent threshold occurs at a photon energy of 0.138 eV, indicating that the Fermi level is pinned close to the valence band. We argue that this is the case only for discrete locations of the interface and suggest that the pinning is caused by a defect-related acceptor level. ©1997 American Institute of Physics.