used these ideas to explain the electroluminescence in SiC as resulting from the injection of carriers across a junction followed by radiative recombination of electrons and holes. However, the observed photon energy was less than the energy gap of SiC, and they suggested that radiative recombination was likely to occur due to impurities or lattice defects. In 1955, injection electroluminescence was shown in a number of III-V compounds [4, 5]. In 1955 and 1956, J.R. Haynes at Bell Telephone Laboratories demonstrated that electroluminescence observed in germanium and silicon was due to recombination of holes and electrons in a p-n junction [6] (see Fig. 1).