A correlation has been established between the optical and structural properties of blue-light-emitting diode structures grown on free-standing m-plane GaN. A double-peak InGaN quantum well emission at room temperature has been observed with a strong inhomogeneous spatial distribution, which can be associated with the presence of dislocations originating at the InGaN layers. It is argued that the difference in peak energy positions is due to in-plane piezoelectric fields within the dislocated regions. © 2011 American Institute of Physics.