Highly efficient GaN-based bipolar cascade LEDs

GaN-based light-emitting diodes (LEDs) exhibit a severe efficiency droop with increasing current. The physical mechanisms behind this droop phenomenon are still under dispute, but most droop models hold the rising carrier density inside the quantum wells responsible. This paper analyses a new approach to circumvent the droop problem by raising the quantum efficiency beyond 100% utilizing multiple tunnel junctions inside the multi-quantum well active region.