Optical anisotropy in ultraviolet InGaNGaN quantum-well light-emitting diodes with a general crystal orientation

The crystal orientation effect on optical anisotropy in ultraviolet InGaNGaN quantum-well (QW) light-emitting diodes are investigated using the non-Markovian gain model with many-body effects. The spontaneous emission for the y′ polarization largely increases with a crystal angle because of the reduction in the spontaneous and piezoelectric polarizations. On the other hand, that for the x′ polarization is shown to reach a maximum near θ=24° and begin to decrease when the crystal angle further increases. The absolute value of the anisotropy rapidly increases with a crystal angle and begins to saturate to be about one when a crystal angle exceeds about 50°. This is because, in the case of QW structures with large crystal angles, the states constituting the topmost valence subband near the band edge become predominantly ∫ Y′ > -like.