Optoelectronic Properties and Applications of Rare-Earth-Doped GaN
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oelectronic Properties and Applications of Rare-Earth-Doped GaN A.J. Steckl and Ü.M. Zavada
The Status and prospects of obtaining stimulated emission in Si:Er are reviewed by Gregorkiewicz and Langer in this is sue and by Coffa et al.' in a previous MRS Bulletin issue. While great progress is being made in enhancing the emission intensity of Er-doped Si, it still experiences significant loss in luminescence efficiency at room temperature, as compared with low temperatures. This thermal quenching was shown by Favennec et al.2 to de-
MRS BULLETIN/SEPTEMBER 1999
crease with the bandgap energy of the semiconductor. Hence w i d e - b a n d g a p semiconductors (WBGSs) are attractive candidates for investigation as hosts for RE doping. Figure 1 shows the bandgap of many semiconductors important for optoelec-
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As discussed in the accompanying articles in this issue of MRS Bulletin, the optical properties of rare-earth (RE) elements have led to many important photonic applications, including solid-state lasers, components for telecommunications (optical-fiber amplifiers, fiber lasers), optical storage devices, and displays. In most of these applications, the host materials for the RE elements are various forms of oxide and nonoxide glasses. The emission can occur at visible or infrared (IR) wavelengths, depending on the elec tronic transitions of the selected RE element and the excitation mechanism. Until recently, the study of semiconductors doped with RE elements such as Pr and Er has concentrated primarily on the lowest excited State as an optically active transition. The presence of transitions at IR wavelengths (1.3 and 1.54 p.m.) that are coincident with minima in the optical dispersion and the loss of silica-based glass fibers utilized in telecommunications, combined with the prospect of Integra tion with semiconductor device technology, has sparked considerable interest.
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Figure 1. Bandgap energy and lattice constant of many semiconductors important for optoelectronics. In the case of SiC and III-N Compounds, both cubic (zincblende) and hexagonal crystal polytypes are shown. For the hexagonal materials, the basal-plane lattice constant is used. The colored regions approximate the bandto-band photoemission corresponding to the bandgap energy.
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Optoelectronic Properties and Applications of Rare-Earth-Doped GaN
of the II-VI Compound semiconductors, the advantages of WBGSs over smallergap semiconductors and glasses include greater chemical stability, carrier generation (to excite the RE ions), and physical stability over a wide temperature ränge. The III-N semiconducting Compounds are of p
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