Polarization of III-nitride blue and ultraviolet light-emitting diodes
نویسندگان
چکیده
Polarization-resolved electroluminescence studies of III-nitride blue and ultraviolet sUVd light-emitting diodes sLEDsd were performed. The LEDs were fabricated on nitride materials grown by metalorganic chemical vapor deposition on sapphire substrates s0001d. Transverse electric sTEd polarization dominates in the InGaN/GaN quantum-well sQWd blue LEDs sl8=458 nmd, whereas transverse magnetic sTMd polarization is dominant in the AlInGaN QW UV LEDs sl=333 nmd. For the case of edge emission in blue LEDs, a ratio sr= I' / Iid of about 1.8:1 was observed between the EL intensities with polarization E'c sTE moded and E ic sTM moded, which corresponds to a degree of polarization ,0.29. The UV LEDs exhibit a ratio r of about 1:2.3, corresponding to a degree of polarization ,0.4. This is due to the fact that the degree of polarization of the bandedge emission of the AlxInyGa1−x−yN active layer changes with Al concentration. The low emission efficiency of nitride UV LEDs is partly related to this polarization property. Possible consequences and ways to enhance UV emitter performances related to this unique polarization property are discussed. © 2005 American Institute of Physics. fDOI: 10.1063/1.1875751g
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