Reconstructions of GaN„0001... and „0001̄... surfaces: Ga-rich metallic structures

Reconstructions of GaN~0001! and ~0001̄! surfaces are studied by scanning tunneling microscopy and spectroscopy, by electron diffraction, by Auger electron spectroscopy, and using first-principles theory. Attention is focused on Ga-rich reconstructions for each surface, which are found to have a metallic character involving significant overlap between Ga valence electrons. The electron counting rule is thus violated for these surfaces, but they nonetheless form minimum energy structures. © 1998 American Vacuum Society. @S0734-211X~98!05404-3#