ON THE OPTICAL BAND-GAP OF ZINC-OXIDE

Three different values (3.1, 3.2, and 3.3 eV) have been reported for t he optical band gap of zinc oxide single crystals at room temperature. By comparing the optical properties of ZnO crystals using a variety o f optical techniques it is concluded that the room temperature band ga p is 3.3 eV and that the other values are attributable to a valence ba nd-donor transition at similar to 3.15 eV that can dominate the optica l absorption when the bulk of a single crystal is probed. (C) 1998 Ame rican Institute of Physics.