We have grown GaN on nearly lattice matched MnO(1 1 1) substrates by pulsed laser deposition (PLD) and characterized their structural properties using reflection high-energy electron diffraction (RHEED), atomic force microscopy (AFM), and grazing incidence-angle X-ray reflectivity (GIXR). RHEED observation has revealed that the single crystal GaN(0 0 0 1) grows on MnO(1 1 1) and its in-plane epitaxial relationship is GaN [1 1 (2) over bar 0]//MnO[1 (1) over bar 0]. The lattice mismatch between GaN and MnO for this alignment is calculated to be 1.6%. From GIXR measurements, the roughness of the hetero-interface between GaN and the MnO substrate was estimated to be 2.3 nm. (C) 2002 Published by Elsevier Science B.V.