We report on the structural, morphological, and optical qualities of thick heteroepitaxial layers grown by metalorganic chemical vapor deposition with various growth conditions for applications in wide-bandgap solar cells. The indium incorporation depending on the growth temperature and indium precursor flow rate and the crystalline and optical qualities of InGaN layers depending on indium mole fraction were investigated. The InGaN layers with high structural and optical qualities were obtained for indium mole fractions, , whereas significant degradation of material qualities was observed for , which is associated with the change of growth mode induced by reduced growth temperature. Stokes shift and microscopic and macroscopic phase separations were also studied. Two types of additional phases besides InGaN matrix, i.e., indium-rich InGaN microstructures and macroscopic InGaN domains, were demonstrated to be suppressed by controlling surface adatom mobility and growth rates.