High-quality InAlGaN alloys, quantum wells and associated light emitting diodes have been grown by metalorganic chemical vapor deposition to produce emitters that operate in the ultraviolet (280-400 nm). In situ reflection and ex situ atomic force microscopy measurements show that InAlGaN epilayers and structures have good surface morphology. InAlGaN epilayers have also a narrow (0 0 0 6) reflection X-ray diffraction rocking curve line width of similar to340 arcsec and a strong band edge photoluminescence (PL) emission peak from 320 to 355 nm at room temperature. Several X-ray satellite peaks were observed from InAlGaN-based quantum well structures, revealing that they were periodic with good interfaces. PL mapping measurements of the quantum well structures show excellent wavelength uniformity over a 2" wafer with a standard deviation of similar to0.4% for structures emitting from 353-372 nm. Ultraviolet light emitting diodes based on the same InAlGaN quantum well structures have an electroluminescence emission at similar to375 nm with a line width of similar to10 nm and an excellent wavelength uniformity of less than I nm across a 2" wafer. (C) 2003 Elsevier Science B.V. All rights reserved.