Large Stokes-like shift in N-polar (000-1) InGaN/GaN multiple-quantum-well light-emitting diodes

N-polar (000-1) (-c-plane) InGaN/GaN light-emitting diodes (LEDs) were grown by metalorganic vapor phase epitaxy, and their optoelectronic properties were evaluated by electroreflectance (ER) and electroluminescence (EL) measurements. In-c-plane LEDs, the emission energy was much lower than that in c-plane LEDs. By comparing EL and ER results, we found that the emission energy was also much lower than the transition energy. The transition energy is in good agreement with X-ray diffraction analysis results. These results indicate that-c-plane LEDs exhibit a larger Stokes-like shift than do c-plane LEDs. This Stokes-like shift is due to the strong potential fluctuation, which is possibly caused by the specific growth patterns of-c-plane III-nitrides. The dominant emission centers of the-c-plane LEDs were suggested to be the localized states of InGaN islands.