This paper describes a study on the effect of InGaN underneath layer (UL) on InGaN/GaN LEDs operating in the spectral range from 425 to 460 nm. Samples were grown by metalorganic vapor phase epitaxy (MOVPE). The In content of the UL is studied in the range of 0-2.7%. Multiple quantum well (MQW) surface morphology and crystal structure were characterized by atomic force microscopy (AFM), high resolution X-ray diffraction (XRD) and secondary ion mass spectroscopy (SIMS). Electroluminescence (EL) intensity was found to increase almost 50% at 20 mA injection current by introducing an optimized UL under the MQW stack in the LED structure. Also a decrease in the full width of half maximum (FWHM) and the blue-shift of the EL spectrum compared to the reference sample were observed in the all UL consisting samples. (c) 2008 Elsevier B.V. All rights reserved.