Point defects and blue LED efficiency: the critical role of indium

The success story of blue light-emitting diodes over the past decade is underpinned by the high internal quantum efficiency (IQE) of the InGaN/GaN quantum wells (QWs) within the active region. Yet this extraordinary IQE can only be achieved by adding an indium-containing layer before the QWs—the “underlayer” (UL). In this work, we evidence that any indium-containing III-nitride layer acts to incorporate surface defects; the UL hence acts as a getter for surface defects to avoid their incorporation into the QWs as IQE-reducing point defects (PDs). We directly observe the reduction in PD-density caused by increasing the UL thickness.