Morphology and surface reconstructions of GaN(1 1 00) surfaces

GaN is grown by plasma assisted molecular beam epitaxy on ZnO(1 1 00) substrates. Well-oriented (1 1 00) GaN surfaces are obtained, and (1 1 01) oriented facets are also observed. On the GaN(1 1 00) surfaces under Ga-rich conditions a surface reconstruction with approximate symmetry of "4×5" is found. A model is proposed in which this reconstruction consists of ≥ 2 monolayers of Ga terminating the GaN surface