Investigation of the hetero-epitaxial growth of InN on a GaAs (1 1 0) substrate was performed by metalorganic vapor phase epitaxy in order to realize the formation of semi-polar InN layer on it. The orientation relationship between InN and GaAs (11 0) was confirmed by 20 - omega and pole figure of X-ray diffraction measurements. It was found that the crystalline orientation strongly depended on the growth temperature; mixed domains of (1 0 (1) over bar 3) and (1 1 (2) over bar 0) InN have been grown on GaAs (1 1 0) surfaces when the growth temperature was below 550 degrees C, while (1 0 (1) over bar 3) semi-polar InN layers could be grown by increasing the growth temperature above 575 degrees C. It was also found that the in-plane anisotropy of semi-polar InN layer was suppressed by increasing the growth temperature. Epitaxial relationship of the InN with the GaAs (1 1 0) substrate was InN (1 0 (1) over bar 3) plane parallel to GaAs (1 1 0) and InN ((2) over bar 1 1 0) plane parallel to GaAs((1) over bar 1 0). 2010 Elsevier B.V. All rights reserved.