A LABORATORY EXPERIMENT WITH BLUE-LIGHT-EMITTING DIODES

We present a laboratory experiment designed to show the main character istics of blue light-emitting diodes. The analyzed devices are based o n III-V nitrides (in which the active layer is a direct band gap In0.0 6Ga0.94N 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, an I-n relation could be established between light emiss ion and device current, with n values related to both the physical str ucture and electroluminescence characteristics of these semiconductors , The spectral response measurements allow us to obtain the peak wavel ength 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 s pectra. However, the same analysis is not possible in the SiC-based de vice due to its extremely low measured luminous intensity values, A co mparison of power conversion efficiency of both devices is also given. (C) 1997 American Association of Physics Teachers.