The polarization degree and emission pattern anisotropy of light emitted from strained (0001)Al(In)GaN heterostructures are studied by modelling. The model considers accurately the nonparabolicity of heavy, light, and split-off hole bands, the relevant modification of their densities of states, as well as the optical matrix element dispersion in the k-space. Accounting for all the above factors provides good agreement of the theoretical predictions with the data reported for both bulk AlGaN alloys grown on sapphire substrates and UV LED structures with Al(In)GaN quantum wells serving as the active regions of the devices. The band-structure modification in Al(In)GaN materials under variation of their composition and elastic strain are found to be the primary factors controlling the polarization degree and emission patterns of TE- and TM-polarized light. The anisotropy of the TM-polarized emission pattern (dependence of the emission intensity on the direction of photon release) and polarization degree of the emitted light are found to be remarkably influenced by the nonparabolicity of the hole bands.
Comparison of the experimental polarization degrees (symbols) with the theoretical ones (lines) calculated for different in-plane strains in light-emitting Al(In)GaN heterostructures.