InxGa1-xN (x > 0.3) films on GaN/sapphire templates were grown by NH3 decomposition catalyst-assisted metalorganic vapor phase epitaxy (CAMOVPE). NiO-based pellets were used as a catalyst. Even at a temperature lower than 500 °C, single-crystal In0.3Ga0.7N films were grown without the incorporation of metallic components (In, Ga) or the cubic phase. In contrast with the case of InN growth using the same catalyst [A. Yamamoto et al., Jpn. J. Appl. Phys. 55, 05FD04 (2016)], no marked grain growth or hydrogen etching was observed in In0.3Ga0.7N. Samples grown at a temperature ≤500 °C showed a full-width at half-maximum of the (0002) X-ray rocking curve as small as 10 arcmin or smaller. The carrier concentration in nominally undoped In0.3Ga0.7N grown using the catalyst was higher by about 4 orders of magnitude than that in conventional MOVPE samples. Secondary ion mass spectroscopy analysis revealed that such a higher carrier concentration was due to the marked reduction in carbon contamination level in the films.