Optical anisotropy in ultraviolet InGaN/GaN quantum-well light-emitting diodes with a general crystal orientation

Abstract

The crystal orientation effect on optical anisotropy in ultraviolet InGaN/GaN 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 theta=24 degrees 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 degrees. 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 vertical bar Y '>-like.