Despite the absence of polarization-induced potential barriers, the nonpolar III-nitride multiple-quantum well (MQW) structures are shown to suffer from strongly inhomogeneous population of active QWs dominated by the QW closest to the N-side of the diode structure. This situation is the opposite of polar structures, where the extreme P-side QW always prevails in optical emission. Inhomogeneity of QW populations in nonpolar structures is supported by QW residual charges and becomes stronger in structures with deeper QWs. Indium incorporation into waveguide and/or barrier layers improves the uniformity of QW injection. (C) 2010 Elsevier Ltd. All rights reserved.