8 March 2014 Characterization of 380nm UV-LEDs grown on free-standing GaN by atmospheric-pressure metal-organic chemical vapor deposition
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Abstract
We reported the defects and optical characterizations of the ultraviolet light-emitting diodes grown on free-standing GaN substrate (FS-GaN) and sapphire. Cross-sectional transmission electron microscopy (TEM) images showed that the total defect densities of grown UV LEDs on FS-GaN and sapphire including edge, screw and mixed type were 3.6×106 cm-2 and 5.5×108 cm-2. When substrate of UV LEDs was changed from sapphire to FS-GaN, it can be clearly found that the crystallography of GaN epilayers was drastically different from that GaN epilayers on sapphire. Besides, the microstructures or indium clustering can be not observed at UV LEDs on FS-GaN from TEM measurement. The internal quantum efficiency of UVLEDs on FS-GaN and sapphire were 34.8 % and 39.4 % respectively, which attributed to indium clustering in multi-layers quantum wells (MQWs) of UV LEDs on sapphire. The relationship between indiumclustering and efficiency droop were investigated by temperature-dependent electroluminescence (TDEL) measurements.
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C. Y. Shieh, Z. Y. Li, H. C. Kuo, J. Y. Chang, G. C. Chi, "Characterization of 380nm UV-LEDs grown on free-standing GaN by atmospheric-pressure metal-organic chemical vapor deposition", Proc. SPIE 8986, Gallium Nitride Materials and Devices IX, 898629 (8 March 2014); doi: 10.1117/12.2039621; https://doi.org/10.1117/12.2039621
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