An InN/GaN multiple quantum well (MQW) with very thin InN well layers that emit a blue wavelength has been grown by metalorganic chemical vapor deposition. The structural and optical properties of the InN/GaN MQW were investigated by high-resolution X-ray diffraction (HRXRD), photoluminescence (PL), and transmission electron microscopy (TEM). The introduction of InN well layers in the MQW makes it possible to grow the active layer with high indium composition and the regularly arranged nanostructures without degrading the crystal quality. It was found that the blue emission using the InN/GaN MQW results in high emission efficiency and an increase in the activation energy, which are ascribed to the strong carrier localization in the nanostructures. In addition, these nanostructures could effectively eliminate the quantum confined stark effect by relaxing the strain by nanostructure formation. (c) 2005 Elsevier B.V. All rights reserved.