8 - Rare Earth Impurities in Wide Gap Semiconductors

Abstract

This chapter presents a review of the luminescence characteristics of wide gap compound semiconductors doped with rare earth atoms. In particular, aspects of rare earth atom incorporation in the semiconductor crystal, photoluminescence properties, and prototype electroluminescent devices are addressed in the chapter. Intra-subshell transitions of 4f electrons in rare earth ions lead to narrow absorption peaks in the ultra-violet, visible, and near-infrared regions of the electromagnetic spectrum. Because it appears that the intensity of the room temperature light emission of these ions depends upon the energy bandgap of the host material, wide gap semiconductors may prove to be the best materials for optoelectronic device applications. Prototype electroluminescent (EL) devices have been fabricated based on both low gap semiconductors and wide gap semiconductors. In general, the emission efficiencies need to be improved. The use of wide gap semiconductors leads to less thermal quenching of the electroluminescence. However, O doped Si does lead to state-of-the-art EL devices. Because of the intense current research in SiC and III–V nitride semiconductors, improvements in the crystal quality and in the processing technology of these materials are likely to occur. Such advances will assist efforts to develop EL devices based on wide gap semiconductors doped with RE ions.