We present a laboratory experiment designed to show the main characteristics of blue light-emitting diodes. The analyzed devices are based on III–V nitrides (in which the active layer is a direct band gap In0.06Ga0.94N alloy) and SiC (where the active layer is the 6H polytype of this semiconductor, which is of an indirect band gap class). From the measurements, anInrelation could be established between light emission and device current, withnvalues related to both the physical structure and electroluminescence characteristics of these semiconductors. The spectral response measurements allow us to obtain the peak wavelength of emission with reasonable precision (449±4 nm in the former one and 470±4 nm in the last one). It is also possible to accurately obtain the band gap value of the active layer in the device based on III–V nitrides (3.18±0.03 eV) by analyzing its electroluminescence spectra. However, the same analysis is not possible in the SiC-based device due to its extremely low measured luminous intensity values. A comparison of power conversion efficiency of both devices is also given.