Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes
The polarization of the in-plane electroluminescence of (0001) orientated (In)(Al)GaN multiple quantum well light emitting diodes in the UV-A and UV-B spectral range has been investigated. The intensity for transverse-electric polarized light relative to the transverse-magnetic polarized light decreases with decreasing emission wavelength. This effect is attributed to the rearrangement of the valence bands at the Γ-point of the Brillouin zone with changing aluminum and indium mole fractions in the (In)(Al)GaN quantum wells. For shorter wavelength the crystal-field split-off hole band moves closer to the conduction band relative to the heavy and light hole bands and as a consequence the transverse-magnetic polarized emission becomes more dominant for deep UV LEDs.
Kolbe, T.; Knauer, A.; Chua, C. L.; Yang, Z. H.; Einfeldt, E.; Vogt, P.; Johnson, N. M.; Weyers, M.; Kneissl, M. Optical polarization characteristics of ultraviolet (In)(Al)GaN multiple quantum well light emitting diodes. Applied Physics Letters. 2010 October 25; 97; 171105.