We report about the optical and structural characterization of m-plane InGaN/GaN multiple quantum well (MQW) structures. All samples were grown on 2-inch LiAlO2 substrates in AIXTRON MOVPE reactors. By lowering the MQW growth temperature, an increase of an indium fraction from 5% to 30% is achieved. High-resolution X-ray diffraction (HRXRD) reciprocal space mapping reveals fully strained growth of the quantum wells. The photoluminescence (PL) peak full width half maximum (FWHM) values increase from similar to 130 to similar to 240 meV at room temperature when the indium fraction rises from 10% to 30%. Also, PL peaks show good wavelength stability for indium contents up to 10% when the excitation intensity is varied by two orders of magnitude. However, at 20% indium and above, a clear excitation intensity-induced peak shift of around 50 meV is detected which is likely caused by indium segregation. Cross-section transmission electron microscopy (TEM) hints at indium fluctuation near extended defects. We conclude that an improved growth process for nonpolar InGaN/GaN MQW is necessary to achieve high-performance long-wavelength light-emitting devices. (C) 2010 Elsevier B.V. All rights reserved.