Large internal quantum efficiency of In-free UV-emitting GaN∕AlGaN quantum-well structures

We have achieved dramatic improvement of the internal quantum efficiency (IQE) for ultraviolet-emitting GaN∕AlGaN quantum-well (QW) structures. Despite a defect density of a few 109cm−2 and the use of an In-free QW we achieve best values for the IQE at room temperature of 26%. Under strong nonresonant excitation, the IQE even increases to 38%. We observe a weak dependence of the IQE on excitation power for our structures. This indicates that similar mechanisms as for GaInN-based light emitters are present.