We have performed a comprehensive investigation of the growth parameter space for the MOVPE of a-plane (1 1 (2) over bar 0) InN on a-plane GaN buffer layers deposited on r-plane (1 (1) over bar 0 2) sapphire substrates. About 0.2 mu m thick a-plane InN epilayers were grown on 1 mu m thick a-plane GaN buffer layers in a close-coupled showerhead reactor. The growth parameters-substrate temperature, reactor pressure, V/III ratio-were systematically varied and their effect on structural, electrical, optical and morphological properties of a-plane InN films were studied. All a-plane InN epilayers show an anisotropy in the in-plane mosaicity. The (1 1 (2) over bar 0) omega-fwhm varies depending on the scattering vector being parallel to the c-direction or the m-direction. The magnitude and nature of this anisotropy is strongly influenced by the growth parameters. In general compared to c-plane InN, we observed a higher growth rate and a slightly higher optimum growth temperature for the a-plane InN epilayers. The optimum growth conditions are found at T=550 degrees C, P=500 Torr, V/III = 11,000, where the omega-fwhm for symmetric (1 1 (2) over bar 0) reflections are 0.83 degrees and 1.04 degrees along [0 0 0 1] and [1 (1) over bar 0 0] directions, respectively, and for the skew-symmetric (1 0 (1) over bar 1) plane is 1.47 degrees. The optimized a-plane InN has a photoluminescence peak emission at 1750 nm (0.71 eV) at low temperature (11 K) and a mobility of 234 cm(2)/V s, carrier concentration 1.4 x 10(19) cm(-3) at room temperature. (C) 2010 Elsevier B.V. All rights reserved.