Electrical Polarization Effects on the Optical Polarization Properties of AlGaN Ultraviolet Light-Emitting Diodes

In this paper, the electrical polarization effects on the optical polarization properties of Al_0.35Ga_0.65N multiple quantum well (MQW) ultraviolet (UV) light-emitting diodes (LEDs) by varying the Al content in AlGaN quantum well (QW) barriers are qualitatively analyzed. Numerical simulation results show that the varied potential barrier height and different polarization-induced electric field resulting from varying the Al content in AlGaN QW barriers have great influence on the transverse electric (TE) and transverse magnetic (TM) emission intensities. Both the TE- and TM-polarized spontaneous emissions from the Al_0.35Ga_0.65N QWs decrease with the increase of the Al content in AlGaN QW barriers, which is attributed to the poor carrier confinement resulting from the more serious band bending effect and the reduced effective potential barrier height in the conduction band, especially, the degree of optical polarization increases with the increase of the Al content in AlGaN QW barriers due to the rearrangement of the valence subbands near the Γ-point of the Brillouin zone. It is consequently concluded that the TE and TM spontaneous emissions and the degree of optical polarization are closely related to the Al content in AlGaN QW barriers of the Al_0.35Ga_0.65N MQW UV LEDs.