We demonstrate photocurrent (PC) spectroscopy of GaInN/GaN multiple quantum well structures with electroluminescence peak wavelengths near 550 nm. Two classes of closely related samples were grown by metal-organic vapor phase epitaxy on c -plane (0001) sapphire substrate. Although nominally identical, one set appears optically transparent while the other appears black to the eye. The PC spectrum of the black sample shows a strong enhancement of absorption at wavelengths longer than 450 nm. In UV microscopy clusters of dark areas are found in the black sample. Such findings are commonly ascribed to areas of Indium phase segregation but require further study. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)