Scanning tunneling microscopy and surface simulation of zinc-blende GaN(001) intrinsic 4x reconstruction:: Linear gallium tetramers? -: art. no. 146102

Scanning tunneling microscopy images confirm electron difraction studies that the zinc-blende GaN(001)-4x reconstruction consists of rows aligned along [110] with a spacing along [1 (2) over bar0] of 4a. Dual-bias imaging shows a 180 degrees shift of the corrugation maximum position between the profiles of empty and occupied states, in agreement with surface simulations based on the 4x1 linear tetramer model of Neugebauer et al. [Phys. Rev. Lett. 80, 3097 (1998)]. Electronic structure calculations predict a surface band gap of 1.1 eV, close to the measured value of 1.14 eV and the previously predicted value (1.2 eV). Despite the successes of this model, high-resolution images reveal an unexpected 3x periodicity (not seen in diffraction) along the [110] row direction, indicating the need for a 4x3 model, and putting into question the existence of linear Ga tetramers.