Europium (Eu) doped nitride semiconductors make it possible to create novel optical devices, led outdoor lighting wholesale as a low threshold lasers and single photon emitters. However, not all europium ions are incorporated in semiconductor optical active site that can be excited through the GaN host. Therefore , it is important to develop methods to selectively incorporate europium ions in higher-efficiency optical sites.
Hiroto Sekiguchi and his colleagues at Toyohashi University of Technology and Hamamatsu Photonics Ltd have improved the emission intensity from europium ions by magnesium co-doping and fabricated red LEDs with europium and magnesium doped active layer grown by ammonia source MBE.
The optimal magnesium co-doping selectively enhanced a specific emission site and contributed to a photoluminescence (PL) intensity increase of more than one order of magnitude. From the ratio of PL integrated intensity at 25 K to that at 300 K, the PL efficiency was determined to be as high as 77%.
On the basis of these results, europium doped GaN based LED commercial lighting wholesale were fabricated. Clear rectification characteristics with a turn-on voltage of 3.2 V were observed and a pure red emission was observed by the naked eye at room temperature. These results suggest that europium and magnesium doped GaN is expected to be utilised for realising new nitride-based light-emitting devices.
This work has been described in the paper, "Red-Light-Emitting Diodes with Site-Selective Eu-Doped GaN Active Layer," by H Sekiguchi et al in Japanese Journal of Applied Physics.
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