Energy barrier heights at the interfaces of metal-aluminum oxide-silicon structures have been measured via internal photoemission as a function of metal electrode material, premetallization annealing treatment, and charge trapping. Barrier heights at the SiSingle Bond signAl2O3 interface were insensitive to gate metal, annealing treatment, and charge trapping. Zero-field energy barriers for the Au, Ni, Al, or Mg and Al2O 3 interfaces were found to be 4.1±0.1, 3.7±0.1, 3.2±0.1, and 2.5±0.1 eV, respectively. Effects of charge trapping on the barrier height were measurable only for the MgSingle Bond signAl 2O3 interface. Annealing treatments had no effects on barrier heights within the accuracy of the measurement technique. © 1974 American Institute of Physics.