Temperature Dependence of Optical Polarization in AlGaN‐Based Multiple Quantum Wells with Emission Wavelengths of 220–260 nm

The optical polarization properties of band‐edge emission in AlGaN‐based multiple quantum wells (MQWs) grown on face‐to‐face‐annealed sputter‐deposited AlN templates are investigated by polarization‐dependent photoluminescence spectroscopy. It is found that luminescence polarized with E || c is predominant in the MQW with an emission wavelength of ≈220 nm, while luminescence polarized with E ⊥ c is predominant in the MQWs with emission wavelengths of about 240 and 260 nm. In addition, the absolute values of the optical polarization degrees (OPDs) of the MQWs with emission wavelengths of ≈220 and 260 nm decrease with increasing temperature. This change can be explained by the thermal redistribution of excitons or carriers between valence bands. Furthermore, the effect of the temperature dependence of the OPD on the evaluation of internal quantum efficiency (IQE) is discussed, and it is found that the change in the OPD with temperature may lead to both overestimation and underestimation of the IQE.