m-Plane GaN was grown selectively by metal-organic chemical vapor deposition (MOCVD) on patterned Si(1 1 2) substrates, where grooves aligned parallel to the Si < 1 1 0 > direction were formed by anisotropic wet etching to expose the vertical Si(1 1 1) facets for growth initiation. The effect of growth conditions (substrate temperature, chamber pressure, and ammonia and trimethylgallium flow rates) on the growth habits of GaN was studied with the aim of achieving coalesced m-plane GaN films. The epitaxial relationship was found to be GaN(1 (1) over bar 0 0) parallel to Si(1 1 2), GaN[0 0 0 1] parallel to si[1 1 -1], GaN[(1) over bar (1) over bar 2 0] parallel to Si[1 (1) over bar 0]. Among all growth parameters, the ammonia flow rate was revealed to be the critical factor determining the growth habits of GaN. The distribution of extended defects, such as stacking faults and dislocations, in the selectively grown GaN were studied by transmission electron microscopy in combination with spatially resolved cathodoluminescence and scanning electron microscopy. Basal-plane stacking faults were found in the nitrogen-wing regions of the laterally overgrown GaN, while gallium-wings were almost free of extended defects, except for the regions near the GaN/Si{1 1 1} vertical sidewall interface, where high dislocation density was observed. (C) 2010 Elsevier B.V. All rights reserved.