Influence of the Growth Substrate on the Internal Quantum Efficiency of Algan/Aln Multiple Quantum Wells Governed by Carrier Localization

The influence of the growth substrate on the internal quantum efficiency (IQE) of deep ultraviolet (UV) light emitting diodes is studied. Two nominally identical Al-rich AlGaN/AlN multi-quantum-well (MQW) structures grown by metalorganic vapour phase epitaxy (MOVPE) on different substrates were investigated. The first MQW structure was grown on a native AlN substrate, while the second one was deposited on an AlN template on sapphire. By the combination of atomic force microscopy (AFM), photoluminescence (PL) and cathodoluminescence (CL) spectroscopy, we demonstrate that the dislocation-mediated spiral growth of MQWs on sapphire results in the more efficient localization of carriers. This effect helps to prevent non-radiative carrier recombination at point defects, improving the IQE of the structure. I.